Scientific American Supplement No. 433

Produced by J. Niehof, D. Kretz, J. Sutherland, and Distributed Proofreaders SCIENTIFIC AMERICAN SUPPLEMENT NO. 433 NEW YORK, APRIL 19, 1884 Scientific American Supplement. Vol. XVII, No. 433. Scientific American established 1845 Scientific American Supplement, $5 a year. Scientific American and Supplement, $7 a year. * * * * * TABLE OF CONTENTS. I. CHEMISTRY,
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Produced by J. Niehof, D. Kretz, J. Sutherland, and Distributed Proofreaders



NEW YORK, APRIL 19, 1884

Scientific American Supplement. Vol. XVII, No. 433.

Scientific American established 1845

Scientific American Supplement, $5 a year.

Scientific American and Supplement, $7 a year.

* * * * *


I. CHEMISTRY, METALLURGY, ETC.–New Analogy between Solids, Liquids, and Gases.

Hydrogen Amalgam.

Treatment of Ores by Electrolysis.–By M. KILIANI.

II. ENGINEERING, AND MECHANICS.–Electric Railway at Vienna.–With engraving.

Instruction in Mechanical Engineering.–Technical and trade education.–A course of study sketched out.–By Prof. R.H. THURSTON.

Improved Double Boiler.–3 figures.

The Gardner Machine Gun.–With three engravings showing the single barrel, two barrel, and five barrel guns.

Climbing Tricycles.

Submarine Explorations.–Voyage of the Talisman.–The Thibaudier sounding apparatus.–With map, diagrams, and engravings.

Jamieson’s Cable Grapnel.–With engraving.

A Threaded Set Collar.

III. TECHNOLOGY.–Wretched Boiler Making.

Pneumatic Malting.–With full description of the most improved methods and apparatus.–Numerous figures.

Reducing and Enlarging Plaster Casts.

Stripping the Film from Gelatine Negatives.

IV. ELECTRICITY.–Non-sparking Key.

New Instruments for Measuring Electric Currents and Electromotive Force.–By MESSRS. K.E. CROMPTON and GISBERT KAPP.–Paper read before the Society of Telegraph Engineers.–With several engravings.

When Does the Electric Shock Become Fatal?

V. ART AND ARCHAEOLOGY.–Robert Cauer’s Statute of Lorelei.–With engraving.

The Pyramids of Meroe.–With engraving.

VI. ASTRONOMY AND METEOROLOGY.–The Red Sky.–Cause of the same explained by the Department of Meteorology.

A Theory of Cometary Phenomena.


VII. NATURAL HISTORY.–The Prolificness of the Oyster.

Coarse Food for Pigs.

VIII. BOTANY, HORTICULTURE, ETC.–Forms of Ivy.–With several engravings.

Propagating Roses.

A Few of the Best Inulas.–With engraving.

Fruit Growing.–By P.H. FOSTER.

IX. MEDICINE, HYGIENE, ETC.–A People without Consumption, and Some Account of Their Country, the Cumberland Tableland. –By E.M. WIGHT.

The Treatment of Habitual Constipation.

X. MISCELLANEOUS.–The French Scientific Station at Cape Horn.

XI. BIOGRAPHY.–The Late Maori Chief, Mete Kingi.–With portrait.

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In 1875 Lieutenant Weyprecht of the Austrian navy called the attention of scientific men to the desirability of having an organized and continual system of hourly meteorological and magnetic observations around the poles. In 1879 the first conference of what was termed the International Polar Congress was held at Hamburg. Delegates from eight nations were present–Germany, Austria, Denmark, France, Holland, Norway, Russia, and Sweden.

The congress then settled upon a programme whose features were: 1. To establish general principles and fixed laws in regard to the pressure of the atmosphere, the distribution and variation of temperature, atmospheric currents, climatic characteristics. 2. To assist the prediction of the course and occurrence of storms. 3. To assist the study of the disturbances of the magnetic elements and their relations to the auroral light and sun spots. 4. To study the distribution of the magnetic force and its secular and other changes. 5. To study the distribution of heat and submarine currents in the polar regions. 6. To obtain certain dimensions in accord with recent methods. Finally, to collect observations and specimens in the domain of zoology, botany, geology, etc.

The representatives of the various nations had several conferences later, and by the 1st of May, 1881, there were sufficient subscribers to justify the establishment of eight Arctic stations.

France entered actively in this work later, and its first expedition was to Orange Bay and Cape Horn, under the surveillance and direction of the Academy of Sciences, Paris, and responsible to the Secretary of the Navy. On the 6th of September, 1882, this scientific corps established itself in Orange Bay, near Cape Horn, and energetically began its serious labors, and by October 22 the greater part of their preliminary preparations was completed, comprising the erection of a magnetic observatory, an astronomic observatory, a room for the determination of the carbonic anhydride of the air, another for the sea register, and a bridge 92 feet long, photographic laboratory, barometer room, and buildings for the men, food, and appurtenances, together with a laboratory of natural history.

In short, in spite of persistent rains and the difficulties of the situation, from September 8 to October 22 they erected an establishment of which the different parts, fastened, as it were, to the flank of a steep hill, covered 450 square meters (4,823 square feet), and rested upon 200 wooden piles.

From September 26, 1882, to September 1, 1883, night and day uninterruptedly, a watch was kept, in which the officers took part, so that the observations might be regularly made and recorded. Every four hours a series of direct magnetic and meteorological observations was made, from hour to hour meteorological notes were taken, the rise and fall of the sea recorded, and these were frequently multiplied by observations every quarter of an hour; the longitude and latitude were exactly determined, a number of additions to the catalogue of the fixed stars for the southern heavens made, and numerous specimens in natural history collected.

The apparatus employed by the expedition for the registration of the magnetic elements was devised by M. Mascart, by which the variations of the three elements are inscribed upon a sheet of paper covered with gelatine bromide, inclination, vertical and horizontal components, with a certainty which is shown by the 330 diurnal curves brought back from the Cape.

The register proper is composed of a clock and a photographic frame which descends its entire length in twenty-four hours, thus causing the sensitized paper to pass behind a horizontal window upon which falls the light reflected by the mirrors of the magnetic instruments. One of those mirrors is fixed, and gives a line of reference; the other is attached to the magnetic bar, whose slightest movements it reproduces upon the sensitized paper. The moments when direct observations were taken were carefully recorded. The magnetic _pavilion_ was made of wood and copper, placed at about fifty-three feet from the dwellings or camp, near the sea, against a wooded hill which shaded it completely; the interior was covered with felt upon all its sides, in order to avoid as much as possible the varying temperatures.

The diurnal amplitude of the declination increased uniformly from the time of their arrival in September up to December, when it obtained its maximum of 7’40”, then diminished to June, when it is no more than 2’20”; from this it increased up to the day of departure. The maximum declination takes place toward 1 P.M., the minimum at 8:50 A.M. The night maxima and minima are not clearly shown except in the southern winter.

The mean diurnal curve brings into prominence the constant diminution of the declination and the much greater importance of the perturbations during the summer months. These means, combined with the 300 absolute determinations, give 4′ as the annual change of the declination.

M. Mascart’s apparatus proved to be wonderfully useful in recording the rapid and slight perturbations of the magnet. Comparisons between the magnetic and atmospheric perturbations gave no result. There was, however, little stormy weather and no auroral displays. This latter phenomenon, according to the English missionaries, is rarely observed in Tierra del Fuego.

The electrometer used at the Cape was founded upon the principle developed by Sir William Thomson. The atmospheric electricity is gathered up by means of a thin thread of water, which flows from a large brass reservoir furnished with a metallic tube 6.5 feet long. The reservoir is placed upon glass supports isolated by sulphuric acid, and is connected to the electrometer by a thread of metal which enters a glass vessel containing sulphuric acid; into the same vessel enters a platinum wire coming from the aluminum needle. Only 3,000 observations were given by the photographic register, due to the fact that the instruments were not fully protected against constant wet and cold.

Besides these observations direct observations of the magnetometer were made, and the absolute determination of the elements of terrestrial magnetism attempted.

On the 17th of November, 1882, a severe magnetic disturbance occurred, lasting from 12 M. until 3 P.M., which in three hours changed the declination 42′. The same perturbation was felt in Europe, and the comparison of the observations in the two hemispheres will prove instructive.

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The total length of this railway, which extended from the Eiskeller in the Schwimmschul-Allee to the northern entrance of the Rotunda, was 1528.3 meters; the gauge was 1 meter, and 60 per cent. of the length consisted of tangents, the remaining 40 per cent. being mostly curves of 250 meters radius. The gradients, three in number, were very small, averaging about 1:750.

Two generating dynamos were used, which were coupled in parallel circuit, but in such a manner that the difference of potential in both machines remained the same at all times. This was accomplished by the well known method of coupling introduced by Siemens and Halske, in which the current of one machine excites the field of the other.

Although the railroad was not built with a view of obtaining a high efficiency, an electro-motive force of only 150 volts being used, a mechanical efficiency of 50 per cent. was nevertheless obtained, both with one generator and one car with thirty passengers, as well as with two generators and two cars with sixty passengers; while with two generators and three cars (two of them having motors) the same result was shown.


The curves obtained by the apparatus that recorded the current showed very plainly the action within the machines when the cars were started or set in motion; at first, the current rose rapidly to a very high figure, and then declined gradually to a fixed point, which corresponded to the regular rate of speed. The tractive power, therefore, increases rapidly to a value far exceeding the frictional resistances, but this surplus energy serves to increase the velocity, and disappears as soon as a uniform velocity is reached.

The average speed, both with one and three cars, was 30 kilometers per hour.–_Zeitsch. f. Elektrotechnik_.

* * * * *


By Professor R. H. THURSTON.

The writer has often been asked by correspondents interested in the matter of technical and trade education to outline a course of instruction in mechanical engineering, such as would represent his idea of a tolerably complete system of preparation for entrance into practice. The synopsis given at the end of this article was prepared in the spring of 1871, when the writer was on duty at the U.S. Naval Academy, as Assistant Professor of Natural and Experimental Philosophy, and, being printed, was submitted to nearly all of the then leading mechanical engineers of the United States, for criticism, and with a request that they would suggest such alterations and improvements as might seem to them best. The result was general approval of the course, substantially as here written. This outline was soon after proposed as a basis for the course of instruction adopted at the Stevens Institute of Technology, at Hoboken, to which institution the writer was at about that time called. He takes pleasure in accepting a suggestion that its publication in the SCIENTIFIC AMERICAN would be of some advantage to many who are interested in the subject.

The course here sketched, as will be evident on examination, includes not only the usual preparatory studies pursued in schools of mechanical engineering, but also advanced courses, such as can only be taught in special schools, and only there when an unusual amount of time can be given to the professional branches, or when post graduate courses can be given supplementary to the general course. The complete course, as here planned, is not taught in any existing school, so far as the writer is aware. In his own lecture room the principal subjects, and especially those of the first part of the work, are presented with tolerable thoroughness; but many of the less essential portions are necessarily greatly abridged. As time can be found for the extension of the course, and as students come forward better prepared for their work, the earlier part of the subject is more and more completely developed, and the advanced portions are taken up in greater and greater detail, each year giving opportunity to advance beyond the limits set during the preceding year.

Some parts of this scheme are evidently introductory to advanced courses of study which are to be taken up by specialists, each one being adapted to the special instruction of a class of students who, while pursuing it, do not usually take up the other and parallel courses. Thus, a course of instruction in Railroad Engineering, a course in Marine Engineering, or a course of study in the engineering of textile manufactures, may be arranged to follow the general course, and the student will enter upon one or another of these advanced courses as his talents, interests, or personal inclinations may dictate. At the Stevens Institute of Technology, two such courses–Electrical and Marine Engineering–are now organized as supplementary of the general course, and are pursued by all students taking the degree of Mechanical Engineer. These courses, as there given, however, are not fairly representative of the idea of the writer, as above expressed, since the time available in general course is far too limited to permit them to be developed beyond the elements, or to be made, in the true sense of the term, advanced professional courses. Such advanced courses as the writer has proposed must be far more extended, and should occupy the whole attention of the student for the time. Such courses should be given in separate departments under the direction of a General Director of the professional courses, who should be competent to determine the extent of each, and to prevent the encroachment of the one upon another; but they should each be under the immediate charge of a specialist capable of giving instruction in the branch assigned to him, in both the theoretical and purely scientific, and the practical and constructive sides of the work. Every such school should be organized in such a manner that one mind, familiar with the theory and the practice of the professional branches taught, should be charged with the duty of giving general direction to the policy of the institution and of directing the several lines of work confided to specialists in the different departments. It is only by careful and complete organization in this, as in every business, that the best work can be done at least expense in time and capital.

In this course of instruction in Mechanical Engineering it will be observed that the writer has incorporated the scheme of a workshop course. This is done, not at all with the idea that a school of mechanical engineering is to be regarded as a “trade school,” but that every engineer should have some acquaintance with the tools and the methods of work upon which the success of his own work is so largely dependent. If the mechanical engineer can acquire such knowledge in the more complete course of instruction of the trade school, either before or after his attendance at the technical school, it will be greatly to his advantage. The technical school has, however, a distinct field; and its province is not to be confounded with that of the trade school. The former is devoted to instruction in the theory and practice of a profession which calls for service upon the men from the latter–which makes demand upon a hundred trades–in the prosecution of its designs. The latter teaches, simply, the practical methods of either of the trades subsidiary to the several branches of engineering, with only so much of science as is essential to the intelligent use of the tools and the successful application of the methods of work of the trade taught. The distinction between the two departments of education, both of which are of comparatively modern date, is not always appreciated in the United States, although always observed in those countries of Europe in which technical and trade education have been longest pursued as essential branches of popular instruction. Throughout France and Germany, every large town has its trade schools, in which the trades most generally pursued in the place are systematically taught; and every large city has its technical school, in which the several professions allied to engineering are studied with special development of those to which the conditions prevailing at the place give most prominence and local importance.

A course of trade instruction, as the writer would organize it, would consist, first, in the teaching of the apprentice the use of the tools of his trade, the nature of its materials, and the construction and operation of the machinery employed in its prosecution. He would next be taught how to shape the simpler geometrical forms in the materials of his trade, getting out a straight prism, a cylinder, a pyramid, or a sphere, of such size and form as may be convenient; getting lines and planes at right angles, or working to miter; practicing the working of his “job” to definite size, and to the forms given by drawings, which drawings should be made by the apprentice himself. When he is able to do good work of this kind, he should attempt larger work, and the construction of parts of structures involving exact fitting and special manipulations. The course, finally, should conclude with exercises in the construction and erection of complete structures and in the making of peculiar details, such as are regarded by the average workman as remarkable “_tours de force_.” The trade school usually gives instruction in the common school branches of education, and especially in drawing, free-hand and mechanical, carrying them as far as the successful prosecution of the trade requires. The higher mathematics, and advanced courses in physics and chemistry, always taught in schools of engineering, are not taught in the trade school, as a rule; although introduced into those larger schools of this class in which the aim is to train managers and proprietors, as well as workmen. This is done in many European schools.

As is seen above, the course of instruction in mechanical engineering includes some trade education. The engineer is dependent upon the machinist, the founder, the patternmaker, and other workers at the trades, for the proper construction of the machinery and structures designed by him. He is himself, in so far as he is an engineer, a designer of constructions, not a constructor. He often combines, however, the functions of the engineer, the builder, the manufacturer, and the dealer, in his own person. No man can carry on, successfully, any business in which he is not at home in every detail, and in which he cannot instruct every subordinate, and cannot show every person employed by him precisely what is wanted, and how the desired result can be best attained. The engineer must, therefore, learn, as soon and as thoroughly as possible, enough of the details of every art and trade, subsidiary to his own department of engineering, to enable him to direct, with intelligence and confidence, every operation that contributes to the success of his work. The school of engineering should therefore be so organized that the young engineer may be taught the elements of every trade which is likely to find important application in his professional work. It cannot be expected that time can be given him to make himself an expert workman, or to acquire the special knowledge of details and the thousand and one useful devices which are an important part of the stock in trade of the skilled workman; but he may very quickly learn enough to facilitate his own work greatly, and to enable him to learn still more, with rapidity and ease, during his later professional life. He must also, usually, learn the essential elements and principles of each of several trades, and must study their relations to his work, and the limitations of his methods of design and construction which they always, to a greater or less extent, cause by their own practical or economical limitations. He will find that his designs, his methods of construction, and of fitting up and erecting, must always be planned with an intelligent regard to the exigencies of the shop, as well as to the aspect of the commercial side of every operation. This extension of trade education for the engineer into several trades, instead of its restriction to a single trade, as is the case in the regular trade school, still further limits the range of his instruction in each. With unusual talent for manipulation, he may acquire considerable knowledge of all the subsidiary trades in a wonderfully short space of time, if he is carefully handled by his instructors, who must evidently be experts, each in his own trade. Even the average man who goes into such schools, following his natural bent, may do well in the shop course, under good arrangements as to time and character of instruction. If a man has not a natural inclination for the business, and a natural aptitude for it, he will make a great mistake if he goes into such a school with the hope of doing creditable work, or of later attaining any desirable position in the profession.

The course of instruction, at the Stevens Institute of Technology, includes instruction in the trades to the extent above indicated. The original plan, as given below, included such a course of trade education for the engineer; but it was not at once introduced. The funds available from an endowment fund crippled by the levying of an enormous “succession tax” by the United States government and by the cost of needed apparatus and of unanticipated expenses, in buildings and in organization, were insufficient to permit the complete organization of this department. A few tools were gathered together; but skilled mechanics could not be employed to take up the work of instruction in the several courses. Little could therefore be done for several years in this direction. In 1875 the writer organized a “mechanical laboratory,” with the purpose of attaining several very important objects: the prosecution of scientific research in the various departments of engineering work; the creation of an organization that should give students an opportunity to learn the methods of research most usefully employed in such investigations; the assistance of members of the profession, and business organizations in the attempt to solve such questions, involving scientific research, as are continually arising in the course of business; the employment of students who had done good work in their college course, when they so desire, in work of investigation with a view to giving them such knowledge of this peculiar line of work as should make them capable of directing such operations elsewhere; and finally, but not least important of all, to secure, by earning money in commercial work of this kind, the funds needed to carry on those departments of the course in engineering that had been, up to that time, less thoroughly organized than seemed desirable. This “laboratory” was organized in 1875, the funds needed being obtained by drawing upon loans offered by friends of the movement and by the “Director.”

It was not until the year 1878, therefore, that it became possible to attempt the organization of the shop course; and it was then only by the writer assuming personal responsibility for its expenses that the plan could be entered upon. As then organized–in the autumn of 1878–a superintendent of the workshop had general direction of the trade department of the school. He was instructed to submit to the writer plans, in detail, for a regular course of shop instruction, and was given as assistants a skilled mechanic of unusual experience and ability, whose compensation was paid from the mechanical laboratory funds, and guaranteed by the writer personally, and another aid whose services were paid for partly by the Institute and partly as above. The pay of the superintendent was similarly assured. This scheme had been barely entered upon when the illness of the writer compelled him to temporarily give up his work, and the direction of the new organization fell into other hands, although the department was carried on, as above, for a year or more after this event occurred.

The plan did not fall through; the course of instruction was incorporated into the college course, and its success was finally assured by the growth of the school and a corresponding growth of its income, and, especially, by the liberality of President Morton, who met expenses to the amount of many thousands of dollars by drawing upon his own bank account. The department was by him completely organized, with an energetic head, and needed support was given in funds and by a force of skilled instructors. This school is now in successful operation. This course now also includes the systematic instruction of students in experimental work, and the objects sought by the writer in the creation of a “mechanical laboratory” are thus more fully attained than they could have possibly been otherwise. It is to be hoped that, at some future time, when the splendid bequest of Mr. Stevens may be supplemented by gifts from other equally philanthropic and intelligent friends of technical education, among the alumni of the school and others, this germ of a trade school maybe developed into a complete institution for instruction in the arts and trades of engineering, and may thus be rendered vastly more useful by meeting the great want, in this locality, of a real trade school, as well as fill the requirements of the establishment of which it forms a part, by giving such trade education as the engineer needs and can get time to acquire.

The establishment of advanced courses of special instruction in the principal branches of mechanical engineering may, if properly “dovetailed” into the organization, be made a means of somewhat relieving the pressure that must be expected to be felt in the attempt to carry out such a course as is outlined below. The post-graduate or other special departments of instruction, in which, for example, railroad engineering, marine engineering, and the engineering of cotton, woolen, or silk manufactures, are to be taught, may be so organized that some of the lectures of the general course may be transferred to them, and the instructors in the latter course thus relieved, while the subjects so taught, being treated by specialists, may be developed more efficiently and more economically.

Outlines of these advanced courses, as well as of the courses in trade instruction comprehended in the full scheme of mechanical engineering courses laid out by the writer a dozen years ago, and as since recast, might be here given, but their presentation would occupy too much space, and they are for the present omitted.

The course of instruction in this branch of engineering, at the Stevens Institute of Technology, is supplemented by “Inspection Tours,” which are undertaken by the graduating class toward the close of the last year, under the guidance of their instructors, in which expeditions they make the round of the leading shops in the country, within a radius of several hundred miles, often, and thus get an idea of what is meant by real business, and obtain some notion of the extent of the field of work into which they are about to enter, as well as of the importance of that work and the standing of their profession among the others of the learned professions with which that of engineering has now come to be classed.

At the close of the course of instruction, as originally proposed, and as now carried out, the student prepares a “graduating thesis,” in which he is expected to show good evidence that he has profited well by the opportunities which have been given him to secure a good professional education. These theses are papers of, usually, considerable extent, and are written upon subjects chosen by the student himself, either with or without consultation with the instructor. The most valuable of these productions are those which present the results of original investigations of problems arising in practice or scientific research in lines bearing upon the work of the engineer. In many cases, the work thus done has been found to be of very great value, supplying information greatly needed in certain departments, and which had previously been entirely wanting, or only partially and unsatisfactorily given by authorities. Other theses of great value present a systematic outline of existing knowledge of some subject which had never before been brought into useful form, or made in any way accessible to the practitioner. In nearly all cases, the student is led to make the investigation by the bent of his own mind, or by the desire to do work that may be of service to him in the practice of his profession. All theses are expected to be made complete and satisfactory to the head of department of Engineering before his signature is appended to the diploma which is finally issued to the graduating student. These preliminaries being completed, and the examinations having been reported as in all respects satisfactory, the degree of Mechanical Engineer is conferred upon the aspirant, and he is thus formally inducted into the ranks of the profession.


Robert H. Thurston–July, 1871.


MATERIALS USED IN ENGINEERING.–Classification, Origin, and Preparation (where not given in course of Technical Chemistry), Uses, Cost.

_Strength and Elasticity_.–Theory (with experimental illustrations), reviewed, and tensile, transverse and torsional resistance determined.

_Forms_ of greatest strength determined. _Testing_ materials.

_Applications_.–Foundations, Framing in wood and metal.

FRICTION.–Discussion from Rational Mechanics, reviewed and extended.

_Lubricants_ treated with materials above.

Experimental determination of “coefficients of friction.”


TOOLS.–Forms for working wood and metals. Principles involved in their use.

Principles of pattern making, moulding, smith and machinists’ work so far as they modify design.

Exercises in Workshops in mechanical manipulation.

Estimates of _cost_ (stock and labor).

MACHINERY AND MILL WORK.–Theory of machines. Construction. Kinematics applied. Stresses, calculated and traced. Work of machines. Selection of materials for the several parts. Determination of _proportions_ of details, and of _forms_ as modified by difficulties of construction.

Regulators, Dynamometers, Pneumatic and Hydraulic machinery. Determining _moduli_ of machines.

POWER, transmission by gearing, belting, water, compressed air, etc.

LOADS, transportation.



_Windmills_, their theory, construction, and application.

_Water Wheels_. Theory, construction, application, testing, and comparison of principal types.

_Air, Gas, and Electric Engines_, similarly treated.

STEAM ENGINES.–Classification. [Marine (merchant) Engine assumed as representative type.] Theory. Construction, including general design, form and proportion of details.

_Boilers_ similarly considered. Estimates of _cost_.

_Comparison_ of principal types of Engines and Boilers. Management and repairing. Testing and recording performance.


MOTORS APPLIED to Mills. Estimation of required power and of _cost_.

Railroads. Study of Railroad machinery.

Ships. Structure of Iron Ships and rudiments of Naval architecture and Ship propulsion.

PLANNING Machine shops, Boiler shops, Foundries, and manufactories of textile fabrics. Estimating _cost_.


GENERAL SUMMARY of principal facts, and natural laws, upon the thorough knowledge of which successful practice is based; and general _resume_ of principles of business which must be familiar to the practicing engineer.




Accompanying the above are courses of instruction in higher mathematics, graphics, physics, chemistry, and the modern languages and literatures.

* * * * *


The operation of boiling substances under pressure with more or less dilute sulphuric or sulphurous acid forms a necessary stage of several important manufactures, such as the production of paper from wood, the extraction of sugar, etc. A serious difficulty attending this process arises from the destructive action of the acid upon the boiler or chamber in which the operation is carried on, and as this vessel, which is generally of large dimensions, is exposed to considerable pressures, it is necessarily constructed of iron or some other sufficiently resisting metal. An ingenious method of avoiding this difficulty has been devised, we believe in Germany, and has been put into practice with a certain amount of success. It consists in lining the iron boiler with a covering of lead, caused by fusion to unite firmly to the walls of the boiler, and thus to protect it from the action of the acid. No trouble, it is stated, is found to arise from the difference in expansion of the two metals, which, moreover, adhere fairly well; but, on the other hand, we believe it does actually occur that the repairs to this lead lining are numerous, tedious, and costly of execution, so that the system can scarcely be regarded as meeting the requirements of the manufacturer. It is to secure all the advantages possessed by a lead-lined vessel, without the drawback of frequent and expensive repairs, that the digester, of which we annex illustrations, has been devised by Mr. George Knowles, of Billiter House, Billiter Street. It consists of a closed iron cylindrical vessel suitable for boiling under pressure, and containing a second vessel open at the top, and of such a diameter as to leave an annular space between it and the walls of the outer shell. This inner receiver, which may be made of lead, glass, pottery, or any other suitable material, contains the substance to be treated and the sulphurous acid or other solution in which it is to be boiled. The annular space between the two vessels is filled with water to the same level as the solution in the receiver, and the latter is provided with suitable pipes or coils, in which steam is caused to circulate for the purpose of raising the solution of the desired temperature, and effecting the digesting process. At the same time any steam generated collects in the upper part of the boiler, and maintains an equal pressure within the whole apparatus. Figs. 1 to 3 show the arrangement clearly. Within the boiler, a, is placed the receiver, b, of pottery, lead, or other material, leaving an annular space between it and the boiler; this space is filled with water. The receiver, b, is furnished with a series of pipes, in which steam or hot water circulates, to heat the charge to the desired temperature. These pipes may be arranged either in coils, as shown at d, Fig. 1, or vertically at d, Fig. 3. The latter are provided with inner return pipes, so that any condensed water accumulating at the bottom may be forced up the inner pipes by the steam pressure and escape at the top. The vessel is charged through the manhole, e, and the hopper, c, provided with a perforated cover, and is discharged at the bottom by the valve, f, shown in Figs. 2 and 3. The upper part of the boiler serves as a steam dome, and the pressure on the liquid in the receiver and on the water in the annular space is thereby maintained uniform. The necessary fittings for showing the pressure in the vessel, water level indicator, safety valve, cocks for testing solutions, etc., are of course added to the apparatus, but are not indicated in the drawing. The arrangement appears to us to possess considerable merit, and we shall refer to it again on another occasion, after experiments have been made to test its efficiency.–_Engineering_.


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The mechanism by which the various functions of loading, firing, and extracting are performed is contained in a rectangular gun metal case, varying in dimensions with the number of barrels in the arm. In the single barrel gun the size of this case is 14 inches in length, 51/2 inches in depth, and 21/2 inches in width. The top of the box is hinged, so that easy access can be had to the mechanism, which consists of a lock, the cartridge carrier, and the devices for actuating them. In the multiple barrel guns, the frames which, with the transverse bar at the end, hold the barrels in place, form the sides of the mechanism chamber, in the front end of which the barrels are screwed. The mechanism is actuated by a cam shaft worked by a hand crank on one side of the chamber. By this means the locks are driven backward and forward, the latter motion forcing the cartridges into place, and the former withdrawing the empty cartridge case after firing. The extractor hook pivoted to the lock plunger rises, as the lock advances, over the rim of the case, but is rigid as the lock is withdrawn, so that the action is a positive one. The cartridges, which are contained in a suitable frame attached to the forward part of the breech chamber, pass through openings in the top plate of the latter, an efficient distribution being secured by means of a valve having a transverse motion. Each cartridge as it falls is brought into the axis of the barrel and the plunger, while the advance motion of the lock forces them into position. In the five-barrel gun illustrated by Fig. 3 the cartridge feeder contains 100 cartridges, in five Vertical rows of 20 cartridges each, and these are kept supplied, when firing, from supplementary holders. Fig. 1 shows the portable rest manufactured by the Gardner Gun Company. It consists of two wrought iron tubes, placed at right angles to each other; the front bar can be easily unlocked, and placed in line with the trail bar, from which project two arms, each provided with a screw that serves for the lateral adjustment of the gun. These screws are so arranged as to allow for an oscillating motion of the gun through any distance up to 15 deg. The tripod mounting, used for naval as well as land purposes, is shown in Fig. 2, which illustrates the two barrel gun complete. The five barrel gun, Fig. 3, is shown mounted on a similar tripod. The length of this weapon over all is 53.5 inches, the barrels (Henry system) are 33 inches long, with seven grooves of a uniform twist of one turn in 22 inches.

[Illustration: Fig. 2.–TWO BARREL GARDNER GUN.]

Gardener’s five barrel gun in the course of one of the trials fired 16,754 rounds with only 24 jams, and in rapid firing reached a maximum of 330 shots in 30 seconds. The two barrel gun fired 6,929 rounds without any jam; the last 3,000 being in 11 minutes 39 seconds, without any cleaning or oiling.–_Engineering_.

[Illustration: Fig. 3.–FIVE BARREL GARDNER GUN.]

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The cycle trade is one which has been developed with great rapidity within the last ten years, and, like all new industries, has called forth a considerable amount of ingenuity and skill on the part of those engaged in it. We cannot help thinking, however, that much of this ingenuity has been misplaced, and that instead of striving after new forms involving considerable complication and weight, it would have been better and more profitable if manufacturers had moderated their aspirations, and aimed at greater simplicity of design; for it must be remembered that cyclists are, as a rule, without the slightest mechanical knowledge, while the machines themselves are subject to very hard usage and considerable wear and tear in traveling over the ordinary roads in this country. We refer, of course, more especially to tricycles, which in one form or another are fast taking the place of bicycles, and which promise to assume an important position in every day locomotion. Hitherto one of the chief objections to the use of the tricycle has been the great difficulty experienced in climbing hills, a very slight ascent being sufficient to tax the powers of the rider to such an extent as to induce if not compel him in most instances to dismount and wheel his machine along by hand until more favorable ground is reached. To obviate this inconvenience many makers have introduced some arrangement of gearing speeds of two powers giving the necessary variation for traveling up hill and on the level. We noticed, however, one machine at the exhibition which seemed to give all that could be desired without any gearing or chains at all. This was a direct action tricycle shown by the National Cycle Company, of Coventry, in which the pressure from the foot is made to bear directly upon the main axle, and so transmitted without loss to the driving wheels on each side, the position of the rider being arranged so that just sufficient load is allowed to fall on the back wheel as to obtain certainty in steerage. The weight of this machine is much less than when gearing is used, and the friction is also considerably reduced, trials with the dynamometer having shown that on a level, smooth road, a pull of 1 lb. readily moved it, while with a rider in the seat 4 lb. was sufficient. On this tricycle any ordinary hill can, it is stated, be ascended with great ease, and as a proof of its power it was exhibited at the Stanley show climbing over a piece of wood 8 in. high, without any momentum whatever. We understand that at the works at Coventry a flight of stairs has been erected, and that no difficulty is experienced in ascending them on one of these machines.–_The Engineer_.

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It was but a few years ago that the idea was prevalent that the seas at great depths were immense solitudes where life exhibited itself under no form, and where an eternal night reigned. To-day, thanks to expeditions undertaken for the purpose of exploring the abysses of the ocean, we know that life manifests itself abundantly over the bottom, and that at a depth of five and six thousand meters light is distributed by innumerable phosphorescent animals. Different nations have endeavored to rival each other in the effort to effect these important discoveries, and several scientific missions have been sent to different points of the globe by the English and American governments. The French likewise have entered with enthusiasm upon this new line of research, and for four consecutive years, thanks to the devoted aid of the ministry of the marine, savants have been enabled to take passage in government vessels that were especially arranged for making submarine explorations.


The first French exploration, which was an experimental trip, was made in 1880 by the Travailleur in the Gulf of Gascogne. Its unhoped for results had so great an importance that the following year the government decided to continue its researches, and the Travailleur was again put at the disposal of Mr. Alph. Milne Edwards and the commission over which he presided. Mr. Edwards traversed the Gulf of Gascogne, visited the coast of Portugal, crossed the Strait of Gibraltar, and explored a great portion of the Mediterranean. In 1882 the same vessel undertook a third mission to the Atlantic Ocean, and as far as to the Canary Islands. The Travailleur, however, being a side-wheel advice-boat designed for doing service at the port of Rochefort, presented none of those qualities that are requisite for performing voyages that are necessarily of long duration. The quantity of coal that could be stored away in her bunkers was consumed in a week, and, after that, she could not sail far from the points where it was possible for her to coal up again. So after her return Mr. Edwards made a request for a ship that was larger, a good sailer, and that was capable of carrying with it a sufficient supply of fuel for remaining a long time at sea, and that was adapted to submarine researches. The Commission indorsed this application, and the Minister of Instruction received it and transmitted it to Admiral Jaureguiberry–the Minister of the Marine–who at once gave orders that the Talisman should be fitted up and put in commission for the new dredging expedition. This vessel, under command of Captain Parfait, who the preceding year had occupied the same position on the Travailleur, left the port of Rochefort on the 1st of June, 1883, having on board Mr. Milne Edwards and the scientific commission that had been appointed by the Minister of Public Instruction. The Talisman explored the coasts of Portugal and Morocco, visited the Canary and Cape Verd Islands, traversed the Sea of Sargasso, and, after a stay of some time at the Azores, returned to France, after exploring on its way the Gulf of Gascogne (Fig.).


The magnificent collections in natural history that were collected on this cruise, and during those of preceding years made by the Travailleur, are, in a few days, to be exhibited at the Museum of Natural History. We think we shall be doing a service to the readers of this journal, in giving them some details as to the organization of the Talisman expedition as well as to the manner in which the dredgings were performed.

[Illustration: FIG.2.–PLAN OF THE VESSEL.]

The vessel, as shown by her plan in Fig. 2, had to undergo important alterations for the cruise that she was to undertake. Her deck was almost completely freed from artillery, since this would have encumbered her too much. Immediately behind the bridge, in the center of the vessel, there were placed two windlasses, one, A, to the right, and the other, B, to the left (Fig. 2). These machines, whose mode of operation will be explained further along, were to serve for raising and lowering the fishing apparatus. A little further back there were constructed two cabins, G and HH. The first of these was designed to serve as a laboratory, and the second was arranged as quarters for the members of the mission.

The sounding apparatus, the Brothergood engine for actuating it, and the electric light apparatus were placed upon the bridge. The operating of the sounding line and of the electric light was therefore entirely independent of that of the dredges. On the foremast, at a height of about two meters, there was placed a crane, F, which was capable of moving according to a horizontal plane. Its apex, as may be seen from the plan of the boat, was capable of projecting beyond the sides of the ship, to the left and right. To this apex was fixed a pulley over which ran the cable that supported the dredges or bag-nets, which latter were thus carried over the boat’s sides.


The preliminary operation in every submarine exploration consists in exactly determining the depth of the sea immediately beneath the vessel. To effect this object different sounding apparatus have been proposed. As the trials that were made of these had shown that each of them possessed quite grave defects, Mr. Thibaudier, an engineer of the navy, installed on board the Talisman last year a new sounding apparatus which had been constructed according to directions of his and which have given results that are marvelous. The apparatus automatically registers the number of meters of wire that is paid out, and as soon as the sounding lead touches bottom, it at once stops of itself. This apparatus is shown in Fig. 4, and a diagram of it is given in Fig. 3, so that its operation may be better understood. The Thibaudier sounding apparatus consists of a pulley, P (Fig. 3), over which is wound 10,000 meters of steel wire one millimeter in diameter. From this pulley, the wire runs over a pulley, B, exactly one meter in circumference; from thence it runs to a carriage, A, which is movable along wooden shears, runs up over a fixed pulley, K, and reaches the sounding lead, S, after traversing a guide, g, where there is a small sheave upon which it can bear, whatever be the inclination of the boat. The wheel, B, carries upon its axle an endless screw that sets in motion two toothed wheels that indicate the number of revolutions that it is making. One of these marks the units and the other the hundredths (Fig. 5). This last is graduated up to 10,000 meters. As every revolution of the wheel, B, corresponds to one meter, the number indicated by the counter represents the depth. Upon the axle of the winding pulley there is a break pulley, p. The brake, f, is maneuvered by a lever, L, at whose extremity there is a cord, C, which is made fast to the carriage, A. When, during the motions due to rolling, the tension of the steel wire that supports the lead diminishes or increases, the carriage slightly rises or falls, and, during these motions, acts more or less upon the brake and consequently regulates the velocity with which the wire unwinds. When the lead touches bottom, the wire, being suddenly relieved from all weight (which is sometimes as much as 70 kilos), instantly stops.


The maneuver of this apparatus may be readily understood. The apparatus and its weights are arranged in the interior of the vessel. A man bears upon the lever, L (Fig. 3), and the counter is set at zero. All being thus arranged, the man lets go of the break, and the unwinding then proceeds until the lead has touched bottom. During the operation of sounding, the boat is kept immovable by means of its engine, so that the wire shall remain as vertical as possible. The bottom being reached, the unwinding suddenly ceases, and there is nothing further to do but read the indication given by the differential counter, this giving the depth.


Near the winding pulley, there is a small auxiliary engine, M, which is then geared with the axle of the said pulley, and which raises the sounding apparatus that has been freed from its weight by a method that will be described further along.

We have endeavored in Fig. 4 to show the aspect of the bridge at the moment when a sounding was about being made. From this engraving (made from a photograph) our readers may obtain a clear idea of the Thibaudier sounding apparatus, and understand how the wheel over which the wire runs is set in motion by the Brothergood engine.–_La Nature_.

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Some improvements have recently been made by Mr. Alexander Glegg and the inventor in the well-known Jamieson grapnel used for raising submerged submarine cables. The chief feature of the grapnel is that the flukes, being jointed at the socket, bend back against a spring when they catch a rock, until the grapnel clears the obstruction, but allow the cable to run home to the crutch between the fluke and base, as shown in the figures. In the older form the cable was liable to get jammed, and cut between the fixed toe or fluke and the longer fluke jointed into it. This is now avoided by embracing the short fluke within the longer one. The shank, formerly screwed into the boss, is now pushed through and kept up against the collar of the boss, by the volute spring, which at the same time presses back the hinged flukes after being displaced by a rock. The shank can now freely swivel round, whereas before it was rigidly fixed. The toes or flukes are now made of soft cast steel, which can be straightened if bent, and the boss is made of cast steel or gun-metal.

[Illustration: JAMIESON’S GRAPNEL.]

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_To the Editor of the Scientific American_:

As long as I have been a reader of the SCIENTIFIC AMERICAN I have been pleased with the manner in which you investigate and explain the cause of any boiler explosion which comes to your knowledge; and I have rejoiced when you heaped merited censure upon the fraudulent boilermaker. In your paper in December last you copied a short article on “Conscience in Boilermaking,” in which the writer, after speaking of the tricks of the boilermaker in using thinner iron for the center sheets than for the others, and in “upsetting” the edges of the plates to make them appear thicker, goes on to say: “We call attention to this, because the discovery of such practice has made serious trouble between the boilermaker and the steam user. We would not believe that there were men so blind to the duties and obligations which rest upon them as to resort to such practice, but the careful inspector finds all such defects, and in time we come to know whose work is carefully and honestly done, and whose is open to suspicion. In States and cities where inspection laws are in force that give the methods and rules by which the safe working pressure of a boiler is calculated, there is no alternative except to follow the rules; and if certain requirements regarding construction are a part of the law, there is no authority or right to depart from it, and yet there are boilermakers who try to force their boilers into such localities when their work is not up to the requirements of the law.”

Now, if some boilermakers are so dishonest as to try and impose upon the locomotive engineer, who they know will carefully examine every part of his boiler, and who is able to detect any flaw, it is not to be expected that the farmer will escape. Nor does he. The great number of explosions of boilers used in thrashing and in other farm work proves that there are boilermakers who “force their boilers into such localities when their work is not up to the requirements of the law.” And the boilermaker, if he be dishonest, is doubly tempted if the broad width of a continent intervenes between him and the farmer for whom his work is intended, and if in the place where the boiler is to be used there are no inspection laws in force. The farmer who lives many miles from a city, and who has no means of testing any boiler he may purchase, is wholly at the mercy of the boilermaker, and must run it until it explodes or time proves it to have been honestly made. Then, again, there are boilermakers who, although making boilers of good iron and of the proper thickness, finish them off so badly that the farmer is put to great inconvenience and expense to put them in working order. Two years ago I purchased a straw-burning engine and boiler made by an Eastern firm. Before it had run ten days the boiler began to leak at the saddle-bolt holes. The engineer tightened the nuts as far as possible, but could not stop the leaks, which at last became so bad that we had to stop work and take the engine to the shop. Upon taking off the saddle and taking out the bolts it was discovered that they were too small for the holes in the boiler, and that they had been wrapped with candle wick and white lead to make them fill the holes, and that a light washer had been put on each bolt between the head and the inside of the boiler. This washer kept the lead in its place, and prevented the boiler from showing a leak when first fired up. The water pipes in the fire-box soon gave out and became utterly useless. Upon inquiring of the patentee of this straw-burning device, who was supposed to have put it in my boiler, he stated that he had had nothing to do with it, but that it was put in by the firm selling these engines, and “as cheaply as possible.” Before I got this boiler and engine in fair running order I had spent hundreds of dollars and had to do entirely away with the water grates.

Last summer, needing another tharshing engine, I was induced to buy one of the same make as my old one, but with a different straw-burning device. The firm who sold it to me agreed that it should have none of the faults of the old one. Well, I got it, and, upon hauling it out to my ranch, and getting up steam, I found it to be much worse than the first one I had bought. The boiler leaked at nearly every hole where a tap had been screwed into it. It took an engineer, a boilermaker, a blacksmith, and a fireman several days to get it in shape so that we could use it at all; and after we did start up, the boilermaker had to be sent for several times to stop new leaks that were continually showing themselves.

I send you by this mail for your inspection one of the saddle bolts and one of the bolts taken out of the piston, and also the certificates of the engineer, boilermaker, and machinist who repaired the boiler. In justice to my fellow-farmers I ought to publish these certificates and the names of these boilermakers to the world, but, for the present at least, I refrain from so doing. These boilermakers will see this article and they will know, if the public does not, for whom it is intended. If it has the effect of making them exercise more care in the construction and fitting up of their engines and boilers, I have not written in vain.


Los Angeles, Cal., March 7,1884.

[The two bolts and the certificates above referred to accompany the letter of Mr. Freeman. We can only wonder how it was that, after having been treated as he relates in the first instance, he should have had any further business with parties who would send out such boilers, for the testimony of the engineer and workmen make the case even stronger than Mr. Freeman has put it.–ED.]

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There are cases where a long screw must be rotated with a traversing nut or other threaded piece traveling on its thread a limited and variable distance. At one time the threaded nut or piece may be required to go almost the entire length of the screw, and at another time a much shorter traverse would be required. In many instances the use of side check nuts is inconvenient, and in some it is impossible. One way of utilizing the nut as a set collar is to drill through its side for a set screw, place it on its screw, pour a little melted Babbitt metal, or drop a short, cold plug of it into the hole, tap the hole, and the tap will force the Babbitt into the threads.

Insert the set screw, and when it acts on the Babbitt metal it will force it with great friction on to the thread without injuring the thread; and when the set screw tension is released, the nut turns freely. A similar and perhaps a better result may be obtained by slotting the hole through the nut as though for the reception of a key. Secure a key (preferably of the same material as the nut) by slight upsetting at its ends, and then thread the nut, key, and all. Place a set screw through the nut over the threaded key, and the job is complete.

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The lethargy in the malting trade, and in all matters relating to malting processes, induced by two centuries of restrictive legislation, is being gradually shaken off by the malting industry under the new law. For many years nearly all improvements in malting processes originated abroad, as numberless Acts of Parliament fettered every process and the use of every implement requisite in a malt-house in this country. The entire removal of these legislative restrictions gives an opportunity for improved processes, which promises to open up a considerable field for engineering work, and to develop a very backward art by the application of scientific principles. The present time is, therefore, one of more material change than malting has ever experienced.

[Illustration: PNEUMATIC MALTING AT TROYES. Fig. 1.]

Of the numerous improvements effected in the past few years, those made by M. Galland in France, and more recently by M. Saladin, are by far the most prominent. M. Galland originated what is known as the pneumatic system eight or nine years ago. This system is carried out at the Maxeville brewery, near Nancy.

[Illustration: PNEUMATIC MALTING AT TROYES. Fig. 2.]

Since that time further improvements have been made by M. Galland; but more recently great advances have been made in the system by M. Saladin. He has developed the practice of the leading principle, and in conjunction with Mr. H. Stopes, of London, has added improved kilns and various mechanical apparatus for performing the work previously done by hand. He has also devised a very ingenious machine for cooling the moist air by which the process is carried on.


At the recent Brewery Exhibition, some of the machinery used in these new maltings was shown in action by Messrs. H. Stopes & Co., together with drawings of a malting constructed at Troyes for M. Bonnette under M. Saladin’s instructions. This malting is the third constructed for the same firm, the others being at Nancy. That at Troyes we now illustrate. We will not occupy space by a general description of the pneumatic system, one great feature in which is the continuous manufacture of malt throughout the year instead of only from five to eight months of the year, as it will be gathered from the following description of the Troyes malting:


In our engravings, Figs. 1, 2, and 3, the letter A indicates the germinating cases; B, Saladin’s patent turning screws; C A, air channels; D, passages; E R, main driving shafts; e, pulleys; F, metal recesses to fit turning screws; G, elevators; H, trap doors; I, air channels; J, openings to growing floor for air; K S, engines and fan room; L N, fans, supply and exhaust; T, boiler; U, chimney; f, well. The capacity of the malting is 130 qr. malt every day. This is equivalent to an English house of 520 qr. steep. The whole space occupied is the area necessary for kilns, malt and barley stores, engine and boiler house, and fans. No additional area is required for germinating floors, as ten germinating cases, A, are placed in the basement below the kilns and stores. The building is of brick, with the internal walls below the ground line resting upon cast iron columns and rolled joists. The germinating cases, A A, are of iron; the bottoms are double. One of perforated plate is placed 6 inches above the bottom. These plates admit of draining the corn if the germinating case is used as a steeping cistern also. Their chief object is, however to admit of ready circulation of the air by the means presently to be described. Large channels, A a, serve as drains for moisture and to convey the air to or from the growing corn. Between each case is a passage, D, enabling the maltster to have free access to the corn at all points.


With the exception of the driving shaft, E, all the machinery is in duplicate, so that the possibility is remote of any breakdown that would seriously affect the working of the house. This is necessary, as should the fans, L N, be stopped for twenty-four hours the corn germinating at a depth exceeding 30 inches would heat and impair its vitality. The boilers, T, and engines, S, are of the common type of 20 horse power nominal. The fans, L N, are the Farcot patent, illustrated a short time since in our pages. The lower floors of the kilns are provided with the Schlemmer patent mechanical turners. The turners, Fig. 4, in the germinating cases are Saladin’s patent.


The germination of the grain is effected by means of cool moist air provided by the fan described and the cooler and moistener–Figs. 5, 6, and 7, herewith–known as an _echangeur_. As the germinating grain has a depth of from 30 inches to 40 inches some pressure is required, and mechanical means are necessary for efficient and economical turning. The _echangeur_ is a very ingenious application of the well understood rapidity of evaporation of any liquid when spread out in very thin layers over large surfaces and exposed to a current of air. It consists of a cylinder, or series of cylinders, of increasing diameter, placed one within another. Each consists of finely perforated sheet iron. They are placed in a trough of water, just sufficiently immersed to insure complete wetting. When rotated at a slow speed, the surfaces of all the cylinders are kept just wetted. A volume of air is either driven or drawn through, as may be required for any particular purpose. In the model malting, as shown at Fig. 4, taken from that shown at the Brewery Exhibition, the air was driven through the _echangeur_ and thence through the germinating barley. Here or as employed in the malting illustrated, the air in its passage comes first into contact with the moistened cylinders, and if hot and dry it becomes moist and cool, for the constant evaporation upon the cylinders has a very considerable refrigerating effect.

This was well known to the Egyptians over four thousand years ago, and the porous bottle–_gergeleh_–of Esnch has been made until the present day, to keep the drinking water cool and fresh. The _echangeur_ is like a gigantic gergeleh, and by increasing the size and number of the cylinders, and causing the water in the moistening trough to circulate, any volume of air can be wetted to the saturation limit corresponding to its temperature. It will be seen that this apparatus gives the maltster complete control of the humidity and heat as well as volume of the air driven through germinating corn.

[Illustration: Fig. 8.]

The turning apparatus is shown by Fig. 4, and consists, as will be seen, of a cylindrical frame provided with rollers which run on rails at the edge of the germinating cases. It is carried to and fro from either end of the case by compensating rope gearing which at the same time gives motion to the gearing actuating the turning screws. These screws do not quite touch the bottom of the germinating case, but are provided with a pair of small brushes, as shown in the annexed engraving, Fig. 8, which just skim it. The apparatus shown has but three of these screws, but the cases are generally made wide enough for six. The kilns are double, each possessing two floors, and worked upon the Stopes’ system. The construction of the furnaces is of the ordinary French pattern. The arrangement of the house permits of great regularity in working. Every day 130 qrs. of barley is screened, sorted, cleaned, and passed into a steeping cistern. When sufficiently steeped it runs through piping into the germinating case, which, in the natural order of working, is empty. Here it forms the couch. When it is desirable to open couch a small amount of air is forced through the grain by opening the trap door connected with the main air channel. This furnishes the growing corn with oxygen, removes the carbonic acid gas, and regulates temperatures of the mass of grain. Later the Saladin turner is put in motion about every eight to twelve hours. The screws in rotating upon their axes are slowly propelled horizontally. They thus effectually turn the grain and leave it perfectly smooth. This turning prevents matting of the roots, the regulation of temperature and exposure to air being effected by means of the cold air from the _echangeur_. When the grain is sufficiently grown it is elevated to the kilns. For forty hours it remains upon the top floor. It is then dropped upon the bottom floor, a further charge of green corn following upon the top floor. The benefit is mutual. The bottom floor is maintained at an even temperature, being virtually plunged in an air bath; free radiation of heat is prevented; the top surface of the malt is necessarily nearly as warm as that next the wires, which in its turn is subject to lower heats than would be necessary if free radiation from the surface was allowed. The top floor is by the intervention of the layer of malt between it and the fire prevented it from coming into direct contact with heat of a dangerous and damaging degree. The same heat which is used to dry one floor, and in an ordinary kiln passes at once into the air as waste, is the best possible description of heat, namely, very slightly moistened heated air, to remove the moisture from the second layer of malt at a low temperature. It is of vital importance to retain this green malt at a low heat so long as any percentage of moisture exceeding, say, 15 per cent, is retained by the corn.

The regulation of temperature is shown by the diagrams, Figs. 9 and 10:

[Illustration: Fig. 9.]

[Illustration: Fig. 10.]

The distribution of the heated air in the kiln is rarely as uniform as is supposed, the temperature of the malt on drying floor being very different at different parts. In illustration of this, the following may be taken from a statement by Mr. Stopes of the results of an examination of the temperatures at different parts of a drying floor in a kiln in Norfolk: “A malting steeping 105 qr. every four days has a kiln 75 feet by 36 feet; an average drying area of under 26 feet per qr. The consequent depth of green malt when loaded is over 10 inches. The total area of air inlets is less than 27 feet super. The air outlet exceeds 117 feet, a ratio of 13 to 3. The capacity of head room equals 44,550 feet cube. The area of each tile is 144 inches, with 546 holes, giving an effective air area of some 32 inches. The ratio of non-effective metallic surface to air space is thus 9 to 2.” The Casella anemometer gave no indications at several points, and fluctuating up and down draughts were observable at many others, especially at two corners and along the center. “The strongest upward draught pulsated with the gusts of wind and ranged from 30 feet to 54 feet per minute, a down draught of equal intensity occurring at intervals at the same spot, notwithstanding the fact that the air was rushing in at the inlets below the floor at the high velocity of 785 feet per minute. The temperatures of the drying malt and superimposed air consequent upon the conditions thus indicated were naturally as follows: At B, the place supposed to be hottest: Heat of malt touching tiles, 216 deg.; heat of malt 1 inch above tiles, 167 deg.; heat of malt 3 inches above tiles 154 deg.; heat of malt 4 inches above tiles, 152 deg.; heat of malt 5 inches above tiles, 142 deg.; heat of malt on surface, 112 deg. At A, the place supposed to be coldest: Heat of malt next tiles, 174 deg.; heat of malt 2 inches above tiles, 143 deg.; heat of malt 4 inches above tiles, 135 deg.; heat of malt on surface, 104 deg.; the heat of the air 3 feet above tiles, 84 deg.; the heat of the air 5 feet above tiles, 82 deg. Fig. 9 shows the temperature at twenty-six points close to the tiles, taken with twelve registered and accurate thermometers in the space of fifteen minutes.” These and other similar tests have led to the conclusion that the best malt drying cannot be done on a single floor.

Fig. 10 is a similar diagram showing the temperatures on a drying floor of kiln at Poole, Dorset, altered to Stopes’ system of drying. The temperature at different depths of the drying grain was as follows: Malt at surface of tiles, 142 deg.; malt at 1 inch above tiles, 142 deg.; malt at 2 inches above tiles, 142 deg.; malt at 4 inches above tiles, 141 deg.; malt on surface, 140 deg.

The advantages of the Saladin system over that hitherto working in Britain are numerous, and are thus enumerated by Messrs. Stopes & Co. who are agents for M. Saladin: The area occupied by the building does not equal one-third of that otherwise required. The actual growing-floor space is only about one-seventh, and the number of workmen is ruled necessarily by the size of the house, but on an average is reduced two-thirds; but the employment of much more power is necessary, and the power is used at more frequent intervals. The use of plant and premises is continuous, the processes of malting being equally well performed during the summer months. The further advantage of this is that brewers secure entire uniformity in age of malt. By the English system the stocks of finished malt necessarily fluctuate largely. All grain is subjected to the same conditions of surrounding air, exposure, and temperature. The volume of air supplied to the germinating corn is entirely under control, as are also its temperature and humidity. When germination is arrested and the green malt is drying, the double kilns insure control of the temperatures of the corn in the kilns. The infrequency of turning the germinating grain benefits the growth of the roots and the development of the plumule, besides saving much labor. No grains are crushed or damaged by the feet or shovels of workmen. The air supplied to the corn can be inexpensively freed from disease germs and impurities. The capital needed for malting can be reduced by the diminished cost of installation, and the reduced stocks of malt on hand. The quality of the malt made is considerably improved. The percentages of acidity are much reduced. The stability of the beer is increased, and a greater percentage of the extractive matter of the barley is obtainable by the brewer.–_The Engineer_.

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Profs. Ayrton and Perry lately described and exhibited before the Physical Society their new ammeters and voltmeters, also a non-sparking key. The well known ammeters and voltmeters of the authors used for electric light work are now constructed so as to dispense with a constant, and give the readings in amperes and volts without calculation. This is effected by constructing the instruments so that there is a falling off in the controlling magnetic field, and a considerable increase in the deflecting magnetic field. The deflections are thus made proportional to the current or E.M.F. measured. The ingenious device of a core or soft iron pole-piece, adjustable between the poles of the horseshoe magnet, is used for this purpose. By means of an ammeter and voltmeter used conjointly, the resistance of part of the circuit, say a lamp or heated wire, can be got by Ohm’s law. Profs. Ayrton and Perry’s non-sparking key is designed to prevent sparking with large currents. It acts by introducing a series of resistance coils determined experimentally one after the other in circuit, thereby cutting off the spark.

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[Footnote: Paper read before the Society of Telegraph Engineers, 14th February, 1884.]

In consequence of the rapid development of that part of electrical science which may be termed “heavy electrical engineering,” reliable measuring instruments specially suitable for the large currents employed in lighting and transmission of energy have become an absolute necessity. As usual, demand has stimulated supply, and many ingenious and useful instruments have been invented, the manufacture of which forms at the present day an important industry. Mr. Shoolbred, in a paper which he recently read before this Society, gave a full and interesting account of the labors of our predecessors in this field. To-day we add to the list then given a class of instruments invented by us, examples of which are now before you on the table. We have preferred to call them current and potential indicators in preference to meters, considering that the latter term, or rather termination, ought to be applied rather to integrating instruments, which the necessities of electric lighting, we believe, will soon bring into extensive use. The principal aim in the design of these indicators has been to obtain instruments which will not alter their calibration in consequence of external disturbing forces. If this object can be attained, then it will be possible to divide the scale of each instrument directly into amperes or volts, as the cause may be, and thus avoid the use of a coefficient of calibration by which the deflection has to be multiplied. This is an important consideration when it is remembered that in many cases these instruments have to be used by unskilled workmen, to whom a multiplication involving the use of demical fractions is a tedious and in some cases even an impossible task.

[Illustration: FIG. 1. FIG. 2.]

All measurements are comparative. We measure weights or forces by comparison with some generally known and accepted unit standard weights, lengths, areas, and volumes, by comparison with a unit length, resistance by a standard ohm, and so forth. In the same way currents could be measured by comparison with a standard current: but this would be a troublesome process, not only on account of the apparatus necessary, but also because it would be a matter of some difficulty to have a standard current always ready for use. In general, measurement by direct comparison with a standard unit is discarded for the more indirect method of measuring not the current itself, but its chemical, mechanical, or magnetic effect. The chemical method is very accurate if a proper density of current through the surface of the electrodes be used,[1] but since it requires a considerable time, and, above all, an absolutely constant current, its use is almost entirely restricted to laboratory work and to the calibration of other instruments. For practical ready use, instruments employing the mechanical or magnetic effect of the current are alone suitable. We weigh, so to speak, the current against the force of a magnet, of a spring, or of gravity. The measurement will be exact if the thing against which we weigh or counterbalance the current itself retains its original standard value. Where permanent magnets or springs are used as a balancing force, this condition of constancy in our weights and measures is not always fully maintained, and to make matters worse, there is no visible sign by which a change, should it have occurred, can be readily detected. A spring may have been overstrained or a steel magnet may have become weakened without showing the least alteration in outward appearance. To overcome this difficulty, the obvious remedy is not to use springs or steel magnets at all, but to substitute for these some other force which should be either absolutely constant, such as the force of gravity, or at least should, vary only within narrow limits, and this in accordance with a definite law. This latter condition can be fulfilled by the employment of electro-magnets.

[Footnote 1: According to recent experiments made by Dr. Hammerl, the density of current in a copper voltameter should be half an ampere per square inch of surface.]

[Illustration: FIG 3.]

To imitate with an electro magnet as nearly as possible a permanent magnet, so that the former can be used to replace the latter, it is necessary that the magnetism in the iron core should remain constant. This could, of course, be done by exciting the electro magnet with a constant current from a separate source. (In a recent note to the Paris Academy of Science, M.E. Ducretet described a galvanometer with steel magnet, which is surrounded by an exciting coil. When recalibration appears necessary, a known standard current from large Daniell cells is sent through this coil during a certain time, and thus the magnet is brought back to its original degree of saturation. M. Ducretet also mentions the use of a soft iron bar instead of a steel magnet, in which case the current from the Daniell cells must be kept on during the time an observation is taken.) But such a system would appear to be too complicated for ready use. Moreover, some sort of indicator would be required by which we could make sure that the exciting current has the normal strength.

[Illustration: FIG 4.]

The plan we adopt is to excite the electro magnet by the whole or a part of the current which is to be measured. Since this current varies, the power exciting the core of the electro magnet must also vary; and since we require the core to have as nearly as possible a permanent magnetic force, we are brought face to face with the question, whether an electro magnet can be constructed that has a constant moment under varying exciting currents. This question has been answered by the well known experiments of Jacobi, Dub, Mueller, Weber, and others. To get an absolutely constant magnetic moment, is not possible, but between certain limits we can get a very near approximation to constancy.


The relation between exciting power and magnetic moment is very complicated, depending not only on the dimensions and shape of the core and the manner of winding, but also on the chemical constitution of the iron of the core. It is not possible, or at least it has hitherto not been found possible, to embody all these various elements into an exact mathematical formula, which would give the magnetic moment as a function of the exciting current; but the above mentioned experiments have shown that within certain limits, and in the neighborhood of the point of saturation, the relation between the two is that of an arc to its geometrical tangent. It will be seen that for large angles the arc increases much slower than the tangent; that is, for strongly excited cores, a very large increase of the exciting current will produce only a slight increase of magnetic moment. If Mueller’s formula were correct for all currents, absolute saturation could only be reached with an infinite current. Whether this be the case or not, it is certain that the greater the exciting current the less will a variation in it affect the magnetic moment of the core. To imitate as nearly as possible permanent steel magnets, it is therefore necessary to use electro magnets, the cores of which are easily saturated. The core should be thin and long and of the horseshoe type; the amount of wire wound round it should be large in comparison with the size of the core.


Here is a magnet partly wound which was used in one of our earliest experiments, but which was a failure on account of having far too much mass in the core in comparison with the amount of copper wire wound round it. Since then we have greatly diminished the iron and increased the copper. The cores of the instruments on the table are composed of two or three No. 18 b.w.g. charcoal iron wires, and are wound with one layer of 0’120 inch wire in the case of the current indicators, and eighteen layers of 0.0139 inch wire in the case of the potential indicator. If from the diagram, Fig. 1, we plot a curve the abscissae of which represent exciting current, and the ordinates magnetic moment of the soft iron core, we find that a considerable portion of the curve is almost a straight and only slightly inclined line. If it, were a horizontal straight line the core would be absolutely saturated, but such as it is, it answers the purpose sufficiently well, for with a variation of exciting current from 10 to 100 amperes the magnetic moment varies but slightly. If a small soft iron or magnetic steel needle, _n s_, be suspended between the poles, S N, of an electro magnet of such proportions as described above, and the current, after exciting the electro magnet, _e e_, be lead round the coils, DD, it will be found that for all currents between 10 and 100 amperes the needle, _n s_, shows a definite deflection for each current. Here we have a galvanometer with permanent calibration. In this case the deflection of the needle will not strictly follow the law of tangents, because the directing power of the electro magnet is not absolutely constant; but whatever the exact ratio between deflection and current may be, it must always remain the same, and to each angle of deflection corresponds one definite strength of current.


The force with which the electro magnet tends to keep the needle in its zero position, that is, in line with the poles, S N, is due partly to the magnetism of the core, which is nearly constant, and partly to the magnetic influence of the coils, _ee_, themselves, which is, of course, simply proportional to the current. The total magnetic force acting on the needle is, therefore, represented by the sum of these two forces, and consequently not nearly so constant as might be desired in order to get a good imitation of a tangent galvanometer with a permanent magnet. In the diagram, Fig. 2, the curve, O A B, represents the magnetic moment of the iron core, the straight line, ODE, that of the exciting coils per se, and the dotted line, O F M, the sum of the two, obtained by adding for every current, O C, the respective ordinates, CD and C A.

CF = CD + CA

The rise of this curve shows that the force which tends to bring the needle back to its zero position increases with the current, though at a slower ratio than the deflecting force of the current. It follows from this that for large currents the increment in the angle of deflection is comparatively small, and the divisions on the scale whereon the current is to be read off would come too near together to allow accurate readings to be taken. In other words, the range of accurate reading in an instrument so constructed would only be limited. But it is very easy to eliminate the magnetic effect of the coils of the electro magnet on the needle, by introducing an opposite magnetic effect, so that only that part of the force remains which belongs to the soft iron core proper. One way of doing this is by surrounding the needle with a coil, the plane of which is at right angles to the line, S N, and coupling this coil in series with the deflecting coil, D D. If the proportions of this transverse coil and the direction of the current through it be properly chosen, its magnetic effect can be made to exactly counterbalance that of the exciting coils, _e e_, without perceptibly weakening the magnetism of the iron core. But instead of employing two coils, one parallel and the other transversely to the zero position of the needle, we can obtain the same result in a more simple manner with one coil only, if this be placed at such an angle that its magnetic effect can be substituted for the combined effects of the two coils. In other words, we set the deflecting coil, D D, at a certain angle to the zero position of the needle.

A similar arrangement, though not precisely for the same purpose, has already been suggested and tried by Messrs. Deprez, Carpentier, Ayrton, and Perry, in galvanometers with permanent steel magnets. If the coil, D D, be so placed, the deflecting force which now acts obliquely can be considered as the resultant of two forces, one acting at right angles to the line, S N, as in an ordinary galvanometer, and the other parallel to this line, but in a sense opposed to the action of the electro magnet and its exciting coils. If the angle of obliquity be so chosen that this latter component exactly equals the magnetic effect of the exciting coils _per se_, an equality which holds good for all currents, then we shall have an almost perfect imitation of a tangent galvanometer with permanent magnets. But we can go a step further than this; we can overbalance the exciting coils by setting the deflecting coil at a greater angle than necessary for the mere elimination of the former, and thus attain that an increase of current results in a slight weakening of the field in which the needle swings, thus allowing the increment of the angle of deflection to be comparatively large even for large currents. In this way it is possible to obtain a more evenly divided scale than in the case when the deflection follows the law of tangents, as in an ordinary tangent galvanometer. This principle of overbalancing the exciting coils is shown on diagram, Fig. 2. The straight line, O G, represents the magnetic effect on the needle of that component of the deflecting force which is parallel, but in sense opposed to S N; as mentioned above, the magnetic effect of the exciting coils is represented by the straight line, O E. The combined effect of these two forces on the needle is represented by the line, O K, the ordinates of which must be deducted from those of the curve, O A B, in order to obtain the total directing force due to each current. This is shown by the curve, O P Q, shown in a thick full line. This curve shows how the directing force or strength of field in which the needle swings decreases with an increasing current. That this does actually take place can easily be proved by experiment.

Fig. 4 shows two curves; the one drawn in a full line is obtained by plotting the deflection in degrees of the needle of a potential indicator as abscissae, and the corresponding electromotive forces measured simultaneously on a standard instrument as ordinates; the dotted line shows what this curve would be with an ordinary tangent galvanometer.

The needle of the potential indicator is mounted at the lower end of a steel axle, to the upper end of which is fastened a light aluminum pointer, whereby the deflection of the needle can be read off on a scale divided directly into volts. The scale is placed within a circular dial plate with glass cover, giving sufficient room for the pointer to swing all round, and the needle is placed within a central tube fitting it closely, which acts as a damper and so makes the instrument almost dead beat. Tube and dial are in one casting. The electro magnet is of horseshoe form fastened to a central tubular stand, which also serves to support the two deflecting coils, one on either side of it. The tube within which the magnetic needle swings is inserted into the stand, which is bored out to the external diameter of the tube. The electro magnet and deflecting coils are wound with from 50 to 100 ohms of fine insulated copper wire, and an additional resistance coil of from 450 to 900 ohms of German silver is added, which can, however, be short circuited by depressing a key when the instrument has to be used for reading low electromotive forces. In this case the indication of the pointer must be divided by ten. If a current be sent through the instrument the wrong way, the needle turns through an angle of 180 deg., and thus brings the pointer to the side of the dial opposite to where the scale is. In this position no reading can be taken, and to facilitate the sending of the current in the right direction a commutator is added, and the same is so coupled up that when the pointer stands over the scale the handle on the commutator points to the positive terminal screw. There is a limit of electromotive force below which the indicator fails to give reliable readings. For instance, an instrument wound with 100 ohms of copper wire and 900 ohms of German silver can be used for electromotive forces varying between 300 and 3 volts, but would not be reliable for measuring less than 3 volts.

For very exact measurements the instrument should be placed north and south, in the same position in which it was calibrated. Two different patterns of current indicators are on the table; one with double needles suspended on a point in the way compass magnets are suspended, the other with one lozenge shaped needle mounted on an axle and pivoted on jewels, in every way similar to the needle of the potential indicator first described.

For measurements of currents from 10 amperes upward, there is no need to employ a complete coil as the deflecting agent; one half-coil or one strip passing close under the needle gives sufficient deflecting force, and thus the construction of the instrument is rendered extremely simple. The current, after entering at one of the flat electrodes, splits in two parts, each part passing round the winding of an electro magnet of horseshoe form, the similar poles of both magnets pointing toward each other and toward the needle. After traversing the winding, the current unites again, and passes through a metal strip close under the needle, and finally out of the instrument by the other electrode, which lies close under that at which the current entered, but is insulated from it by a sheet of fiber. The metal strip is set at an angle, to balance or overbalance, as may be preferred, the magnetic influence of the exciting coils. The effect of this overbalancing is shown in Fig. 5, where the full curve represents the current as a function of the deflection–obtained by comparison with a standard instrument–and the dotted curve shows what that relation between deflection and current would be if the law of tangents held good for these instruments. It will be seen that, about the middle of the scale, the dotted line coincides nearly with the full line, while at the extreme end of the scale the dotted line is higher. From this follows, that if we compare our indicator from which this curve was taken with any form of tangent instrument showing an equal angle of deflection at the medium reading, it will be seen that the needle of our indicator will be deflected to a greater angle at high readings than that of the tangent galvanometer. Consequently, the divisions on the scale will be widest apart in our instruments, which greatly facilitates high readings.

* * * * *


The Consolidated Electric Light Company has now completed the secondary battery which has for some time engaged the attention of its officers, and their regular manufacture and use for electric lighting stations have been fairly entered upon. Among other places to which the batteries have been sent and put into work is Colchester, where the company has for some time had an installation at work, chiefly employing incandescent lamps. The battery consists of lead electrodes, anode and cathode being of the same character. They are constructed of narrow ribbons of lead, each element being made from long lengths of the ribbon about or nearly 0.20 in. width, rolled together into a flat cake like rolls of narrow webbing, as illustrated by the annexed diagram, Fig. 1, the greater part of the ribbon being very thin and flat; but intermediate thicker ribbons are also employed, as in Fig. 2, this thicker ribbon being corrugated as shown, and affording passage room for the circulation of the electrolyte. From four to eight coils of the plain ribbons are between every pair of corrugated ribbons. They are wound up together tightly, and pressed into the nearly rectangular form shown. The bar for suspending the coil plates so made in the cells is soldered to the coil. The object of this construction is of course to obtain large lead surface, and of course a much larger surface is so obtained than could be practically obtained from plain lead plates in the same compass. A battery thus made may be seen at the offices of the company, 110 Cannon Street.

[Illustration: FIG. 1. FIG. 2.]

A very ingenious device for cutting the battery out of circuit when charged as much as is thought desirable is used by the company. In a cell is an element which has a determined lower capacity than those in the rest of the battery. Over this element is placed a gas-tight chamber in which is a diaphgram, this diaphragm being of very flexible material placed in the cover of the box of cells. When charging has proceeded as long as is desirable, or proceeds too fast, hydrogen is evolved, and this collecting in the chamber referred to acts upon the diaphragm, and by means of a rod connected thereto, switches the current, which is supplied to an electro-magnet and by which circuit is made through the medium of mercury contacts. The object, of this is to save the battery from destruction by over-charging or charging by too large a current.–_The Engineer_.

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P. CAZENEUVE publishes in the _Comptes Rendus_ a new method for the preparation of acetylene, which consists in mixing iodoform intimately with moist and finely divided silver. An abundant evolution of acetylene takes place without heating. The reaction is represented by the following formula: 2CHI_{3} + 6Ag = C_{2}H_{2} + 6 AgI. The decomposition of the iodoform is hastened if the silver is mixed with finely divided copper, such as can be obtained by precipitating it from its sulphate by means of zinc.

Cazeneuve also observed that most metals which have any affinity for iodine will decompose iodoform in the presence of water, forming acetylene and an iodide of the metal. By the use of zinc he obtained a liquid having a pleasant ethereal odor, and a gas mixture that contained besides acetylene an iodine compound which burned with a purple-edged, fawn-colored flame.

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In this age of electricity and electric wires carrying currents of various intensity, the question of danger arising from contact with them has caused considerable discussion. An examination into the facts as they exist may therefore enlighten some who are at present in the dark.

To begin with, we often hear the question asked–why is it that certain wires carrying very large currents give very little shock, whereas others, with very small currents, may prove fatal to those coming in contact with them? The answer to this is–that the shock a person experiences does not depend upon the current _flowing in the wires_, but upon the current _diverted from them_ and _flowing through the body_.

The muscular contraction due to a galvanic current, which was first observed in the frog, gives a good illustration of the fact that it requires only a very minute current to flow through the muscles in order to contract them. Thus the simple contact of pieces of zinc and copper with the nerves generated current sufficient to excite the muscles–a current which would require a delicate galvanometer for its detection. What is true of the muscles of the frog holds good also for the human muscles; they too are very susceptible to the passage of a current.

In order to determine the current which proves fatal we need only to apply the formula which expresses Ohm’s law, viz., C=E/R, or the current (ampere) equals the electromotive force (volt) divided by the resistance (ohm).

According to the committee of Parliament investigation, the electromotive force dangerous to life is about 300 volts; this then is the quantity, E, in the formula. There remains now only to determine the resistance in ohms which the body offers to the passage of the current. In order to obtain this, a series of measurements under different conditions were made. On account of the nature of the experiment a high resistance Thomson reflecting galvanometer was used, with the following results.

When the hands had been wiped perfectly dry, the resistance of the body was about 30,000 ohms; with the hands perspiring ordinarily it fell to 10,000 ohms; whereas when they were dripping wet it was as low as 7,000 ohms. Our readers can judge this resistance best when we state that the Atlantic cable offers a resistance of 8,000 ohms.

Taking an ordinary condition of the body, with the hands perspiring as usual, we would have the resistance equal to 10,000 ohms. Applying the two known quantities in the formula, we get:

C = (300 / 10,000) – (1 / 33.333+)

This means, therefore, that when the electromotive force or potential is great enough to send a current of 1/33 ampere through the body, fatal results will ensue. This current is so minute that it would deposit only about 6 _grains_ of copper in _one hour_, a grain being 1/7,000 of a pound.

Let us now compare these figures with some actual cases, taking as an example a system of incandescent lighting. In these systems the difference of potential between any two points of the circuit outside of the lamps does not exceed 150 volts. Taking this figure, therefore, it will be seen that under no circumstances can the shock received from touching these wires become dangerous–not even by touching the terminals of the dynamo itself; because in neither case can a current be driven through the body, sufficient to cause an excessive contraction of the muscles.

In a system of arc lighting, however, we have to deal with entirely different conditions; for, while in the incandescent system the adding of a lamp, which diminishes the resistance, requires no increase of electromotive force, the contrary is the case in the arc light system. Here every additional lamp added to the circuit means an increase in resistance, and consequent increase in electromotive force or potential. Taking for example a well known system of arc lighting, we find that the lamps require individually an electromotive force of 40 volts with a current of 10 amperes. In other words, the difference in potential at the two terminals of every such lamp is 40 volts. Consequently, if the circuit were touched in two places, including between them only one lamp, no injurious effects would ensue. If we touch the circuit so as to include two lamps between us, the effect would be greater, since the potential between those two points is 2 x 40 volts. We might continue in this manner touching the circuit until we had included about 7 or 8 lamps, when the shock would become fatal, since the point would be reached at which the difference of potential is great enough to send a dangerous current through the body.

Up to this point we have assumed that, while touching two points in the wire, the rest of the circuit is perfectly insulated, so that no current can leak, in other words, that the circuit is nowhere “grounded.” If this is not the case we may, under suitable conditions, receive a shock by touching only _one_ point of the wire. This becomes clear by considering the current to leak from another spot of different potential, to pass through the ground and into the body; thus, on touching the wire the body virtually makes a connection between the two points of the circuit. In clear dry weather such leaks are insignificant; but in damp and rainy weather, and with poor insulation, they may rise to such a point at which it would be dangerous to touch the circuit even with one hand, the leaks being sometimes so great as to cause the lamps to burn in a fitful, desultory manner, and to go out entirely.

There is still another factor which enters into the discussion of the danger of electric light wires. This must be looked for in the fact that the physiological effects are greatest at the moment of the opening or the closing of the circuit; or in a closed circuit they are the more marked when the flow of current stops and starts, or diminishes and increases. In dynamo electric machines the current is not absolutely continuous or uniform, since the coils on the armature being separated a distance cause a slight break or diminution of the current between each. This break is so short that it does not interfere with the practical work for lighting; in some constructions, nevertheless, the distances apart is so great that, while not interfering with light, its effects upon the muscles are greatly increased over those of other constructions which give a more uniform current.

All these statements might lead to the conclusion that arc light wires are dangerous under any circumstances; but this is not the case. The first and only requisite is, that they be perfectly insulated. When thus protected accidents from them are impossible, and all mishaps that have occurred through them can be traced directly to the lack of insulation. Nevertheless, we would warn our readers against experimenting upon arc wires by actual trial, because unforeseen conditions might lead to disagreeable results.

* * * * *


The statue of Lorelei, the mythical siren of the Rhine, represented in the annexed cut, which is taken from the _Illustrirte Zeitung_, was modeled by Robert Cauer, of Kreuglach on the Rhine. He was born at Dresden in 1831, and is the son of the well-known sculptor Emil Cauer, and a brother of the sculptor Karl Cauer.


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Ordinary casts taken in plaster vary somewhat, owing to the shrinkage of the plaster; but it has hitherto not been possible to regulate this so as to produce any desired change and yet preserve the proportions. Hoeger, of Gmuend, has, however, recently devised an ingenious method for making copies in any material, either reduced or enlarged, without distortion.

The original is first surrounded with a case or frame of sheet metal or other suitable material, and a negative cast is taken with some elastic material, if there are undercuts; the inventor uses agar-agar. The usual negative or mould having been obtained as usual, he prepares a gelatine mass resembling the hektograph mass, by soaking the gelatine first, then melting it and adding enough of any inorganic powdered substance to give it some stability. This is poured into the mould, which is previously moistened with glycerine to prevent adhesion. When cold, the gelatine cast is taken from the mould, and is, of course, the same size as the original. If the copy is to be reduced, this gelatine cast is put in strong alcohol and left entirely covered with it. It then begins to shrink and contract with the greatest uniformity. When the desired reduction has taken place, the cast is removed from its bath. From this reduced copy a cast is taken as usual. As there is a limit to the shrinkage of the gelatine cast, when a considerable reduction is desired