Imágenes de páginas
PDF
EPUB

A Correction.

In last week's Science, p. 256, first column, line 40, occurs a typographical error which it may be worth while to correct.

I refer to the word 'eidography,' erroneously printed 'cidography,' - a word suggested as useful in discussing surveys, and having reference solely to the surface form of the earth, its ups and downs, its hills and hollows. The words 'hypsography' and 'topography' are each used for this purpose; but the first refers rather to elevation than to form, and topography' has been and is used in different senses, hence its meaning is uncertain until defined by the writer using it. MARCUS BAKER.

Washington, D.C., Dec. 4.

Queries.

39. WHAT IS THE ORIGIN OF FISH IN ISOLATED PONDS? -The Peninsula of Florida contains innumerable isolated ponds varying from a few square rods to many square miles in area. Many of these are simple hollows filled with rain-water, without any connection with other waters. Some of them are on high ground, where no flood can establish temporary connection with other waters, through which fish might be admitted. The smaller ones often dry up entirely in seasons of drought, yet when filled with water they do not seem to be behind their neighbors in population. They all swarm with fish, whose origin and continued presence would seem to present an interesting question. For instance at Orange Heights, in Eastern Alachua County, which is one of the most elevated regions of the State, as is plainly shown by the radiating streams which rise in that vicinity, there is a small pond on top of the highest elevation in all that region. I have twice known this pond to be dry, yet it now contains an abundance

IN THE SELECTION OF

of small fish. How have they been preserved from destruction, and whence came the original stock? CHS. B. PALMER. Columbus, O., Nov. 20.

40. FELSPAR, OR FELDSPAR? - Will you or some one of your numerous correspondents kindly inform me which is the more correct designation, 'felspar' or 'feldspar'? Both forms are in common use among mineralogists, and most dictionaries give both. Phillips, in his Elementary Mineralogy,' 1823, gives 'felspar' in the text, and in a footnote feldspar,' from the German feldspath, adding, "perhaps because found on the surface of some parts of the country." Might it not rather be derived from the German fels, 'a rock'? If one knew when and how it was first used, this might solve the point. J. THORBURN.

Ottawa, Can., Nov. 29.

41. THE "SUPERNUMERARY MOLAR" IN MAN. Not many days ago there was a very excellent young dentist at work at Fort Wingate, N. Mex., and while there a white man of some thirty-five years of age presented himself to have extracted what he termed "an extra tooth" in his upper jaw. Happening in, I saw this rare anatomical structure immediately after its removal. It was a small, transversely ellipsoidal tooth, with a single, conical, peg-like fang, the tooth itself having developed at its buccal aspect a small additional cusp. This tooth was situated directly posterior to the upper wisdom tooth or last molar of the left side, and in contact with it. I am aware that this rare supernumerary molar in man is alluded to in the more extensive works upon dentistry, but I would be glad if some reader of this notice will inform me where I may find the best biological account of this structure in man, as well as its significance, and whether it has ever been observed in any of the Simiina. R. W. SHUFEldt.

Fort Wingate, N. Mex., Dec. 1.

A CHOICE GIFT SCIENTIFIC BOOKS.

[graphic]
[blocks in formation]

Catalogue of Books relating to Civil, Mechanical, Electrical, and Mine Engineering, and Manufacturing Industries sent free to any address.

E. & F. N. SPON,

12 Cortlandt Street, New York.

W. H. WALMSLEY & CO.

SUCCESSORS TO

R. & J. BECK,
1016 Chestnut Street Phila

Microscopes and all
Accessories and Ap-
paratus. Photograph-
ic and Photo-Micro-
graphic Apparatus and
Outfits.

Spectacles, Eye
Glasses, Opera and
Marine Glasses, etc.

Illustrated Price List
mailed free to any ad-
dress. Mention SCIENCE
in corresponding with us.

J. GRUNOW,

621 Sixth Avenue, New York.
Established 1852.

MAKER OF

Microscope Stands, Oil Immersion Object

ives and Abbe Con

[blocks in formation]
[graphic]
[graphic]
[blocks in formation]
[graphic]
[blocks in formation]

FRIDAY, DECEMBER 14, 1888.

ELECTRIC PROPULSION.

Nov. 26 and Dec. 5 of the current year will be memorable dates in the history of electric propulsion; for on those days the largest and most powerful electric railway-motor yet constructed gave proof, on the Ninth Avenue line of the New York elevated railways, of its capability to do all that the steam-locomotives there in use are called upon to perform in their regular service. This motor was the Daft motor Benjamin Franklin,' whose plan and side-elevation illustrate this article.

Electrical traction on a minor scale is no new thing: Siemens, at Berlin and Port Rush, had accomplished it as early as 1881, and Daft himself had achieved the first commercial success in this line

The question will naturally suggest itself, What future has this motor, and what are its claims to preference over the system now in use on the New York elevated railways?'

The answer is, radical economy, which lies in the recognized wastefulness of small- especially locomotive - engines, and the high efficiency of large stationary engines of improved type. Multiplication of power-generators implies loss in efficiency, and increased cost of attendance. Derivation of power from one origin, with ready capability of subdivision, is economy. The average consumption of coal per horse-power, as between light rapid express and slow heavy freight-trains, is about nine pounds per hour for steam-locomotives. A modern compound condensing engine will yield a horse-power for two pounds per hour, or even less. Admitting that the conversions from power to current, and vice versa, consume one-third of this, it still remains that the locomo

[graphic][subsumed][merged small][merged small]

A general description of this motor follows; and the cuts will give a clear idea of its mechanical arrangement and details. The total weight is ten tons, - very little over half the weight of the steam-locomotives in regular use, and the wheel-base and length over all are respectively 5' 6" and 14'6". The total horse-power is probably 150, although there has as yet been no opportunity of making an ultimate test in this respect.

The Franklin' was designed to pull four cars and their seated load - a total weight of 75 tons - over any gradient of the Ninth Avenue Elevated Railway at the schedule speed of ordinary trains. In the trials a train of eight empty cars - a load of 122 tons, 47 in excess of that agreed upon - was taken up the maximum gradient (nearly two per cent) at a speed of 7 miles per hour, and a loaded four-car train exceeded the schedule speed by almost 3 miles per hour.

tive-engine needs more than three times as much coal as the stationary for every horse-power exerted upon the track. It is demonstrable that the New York elevated railroads can be run at less than half the present cost for motive power, including a charge for interest on the cost of the new equipment, and ignoring the proceeds derivable from the sale of the old. Other economical features of the system are, 1. Reduction of attendance.

[ocr errors]

2. Conservation of permanent way from the diminution in weight of motor permitted by its superior adhesion. This is always available where the rails constitute part of the circuit, and makes plain why the 'Franklin,' of half the weight of a steam-locomotive, can haul as great a load. One of the most invaluable features of the system is the high degree of adhesion between the motor-wheels and the rails, which permits the employment of much lighter tractors than would be practicable if steam-locomotives were used, to the manifest advantage of the vehicles themselves and of the permanent way. This adhesion is not magnetic, and probably results from molecular change produced by the current in contiguous surfaces of wheel and rail. It sometimes amounts to forty per cent of the weight as opposed to twenty per cent usually observable in steam

locomotives as the average of all conditions of track as affected by weather and use.

3. The possibility of dispensing with the complicated methods of insulation that are necessary and most expensive features of highpotential systems.

4. A potent cause of the economical working of electric railways is found in the capacity for instantaneous adjustment of the current to demands made upon it. This is so marked in the case of a double-track road with the same number of trains moving in both directions, and all deriving their power from a common generatingstation, as to prompt Dr. C. A. Siemens to draw this striking analogy. He declares that two trains on the same track, one descending and the other ascending a gradient, are in as absolute connection by the current in the rails as if tied together by an actual rope. The counter-current generated by the free revolution of the dynamo of the descending train re-enforces the main current, and thus helps the ascending. The result of this is that the maximum capacity of the generating-station need only equal the average work of one motor multiplied by their total number. This will always prove sufficient. Every steam-locomotive must be ready at all times to exert its full power; and the waste of this, in the aggregate, is

enormous.

familiar steam-engine, which has profited by eighty years of use, experiment, and analysis by the best human ingenuity.

To resort to generalization, the steam-engine's characteristic function is to transform heat into mechanical work; and the labor and thought of three generations have only succeeded in recovering, in the shape of work, from ten to twenty per cent of the total heat applied to it. The peculiar office of the dynamo-electric machine is the conversion of mechanical work into current electricity; and in the first decade of its useful existence it returns, in the form of electrical current, ninety per cent of the mechanical work applied to it. The adept steam-engine attains one-tenth of its possible efficiency; the tyro dynamo-electric machine, nine-tenths. "If they do these things in a green tree, what shall be done in the dry?"

ELECTRICAL POWER-DISTRIBUTION.

ONE of M. Victor Popp's friends was recently describing with post-prandial eloquence the wonderful system of compressed-air distribution now so extensively operated in Paris. As if it were not marvellous enough to picture to his hearers' minds pneumatic clocks throughout Paris, and all sorts of machinery deriving power from a central station for compressing air, the interesting 'diner

[graphic][ocr errors][merged small]

The following facts are significant as regards electrical propulsion : 1. The production, by modern stationary engines of the highest efficiency, of a horse-power for two pounds of coal, or less, per hour; 2. A recovery, in kind, from an electric circuit of reasonable length, of at least sixty-five per cent of the mechanical power applied to it; 3. The consumption by small stationary and locomotive engines of from seven to nine pounds of coal per horse-power per hour; 4. The consequent development in the circuit of a horsepower for three pounds of coal as opposed to seven or nine; 5. A marked reduction in original and current cost of motive power, due to lessened weight, simplicity, and diminished attendance; 6. A notably lower rate of deterioration than other machinery, due to the use of low-potential currents, absence of reciprocatory motion, etc.; 7. Conservation of permanent way, arising from the lessened weight of motor due to superior natural adhesion and the power of increasing the same magnetically to any necessary degree; 8. A unique economy arising from the fact that there is no necessity of having superfluous power in reserve, a consequence of the capacity for instantaneous adjustment of a current throughout an entire circuit to the demands made upon it.

[ocr errors]

If one may judge by comparison with other mechanisms, the future of the dynamo-electric motor is pregnant with possibilities. The measure of perfection of any machine is the degree of efficiency with which it performs its specific work. Referred to such a criterion, dynamo-electric machinery stands, at the very starting-post of its career, infinitely nearer to its theoretical ultimate than the

[ocr errors]

FRANKLIN,'

out' added with a most graceful gesture, "Why, messieurs, with the Popp system you freeze the dead bodies in the morgue, and you cremate them in Pere la Chaise." And thus the idea is continually forced upon one's mind that this is an age of centralization in the supply of heat, water, light, and power, and, in fine, every thing that makes life more comfortable, and business more practicable. The application of electricity to the distribution of power has been developed with comparatively more marked progress than the electric-lighting industry met with in the early stages of its existence; and this is not strange, when we consider the advantages of electric motors, and the fact that their use makes a material difference with small manufacturers in the item of cost of power, besides constituting an important feature of safety. The fact that the noisy, dusty, and dangerous steam-engines which are being used in so many printing-offices, book-binderies, and various other shops where power is needed, may be displaced by quietrunning electric motors, which are not dangerous and do not take up much room, added to the actual saving in money which is accomplished by such a change, are points which are so easy of demonstration, and commend themselves so readily to the popular mind, that the introduction of electric motors has not met with any serious obstacles. Although the first experimenters built motors before they built dynamos, it is only within the last two or three years that practical machines of a high efficiency have been offered to the public. Some of the machines now give an efficiency of over ninety per cent in the conversion of electrical into mechanical

energy; and it is plain that there is no possibility of very much improvement in the efficiency of conversion. The regulation of the electric motor is accomplished in some cases by artificial means; but in the most approved type of electric motors the regulation is in the machine itself, and depends upon an electrical principle as interesting and wonderful as any fact in the whole range of the science. Comparatively speaking, it is this. Dynamos and motors are interchangeable: when we put mechanical power to the machine, and make thereby electrical power for further use, we call the apparatus a dynamo-electric machine; if we reverse the process, however, and bring forth mechanical power by putting a cur

motor take up its increased load. The change in the electrical condition is practically instantaneous, so that no change in the speed of the motor is perceptible within the moderate changes in the work which it is doing. With a maximum change in the load: which the motor is carrying, the variation of the speed of the motor is within two per cent of its normal speed. Such close regulation, it is needless to say, is all that can be desired in any machine. The motors of the Thomson-Houston Electric Company, like all the other apparatus of that system, have been widely introduced, and are in use in many printing-offices, machine-shops, and small factories. They are made in sizes to furnish from one-half to seventy-five

[graphic][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][merged small]

rent of electricity through a machine, it becomes an electric motor. Every motor, while receiving the electric current and doing mechanical work, is at the same time retaining to some degree its character as a dynamo-machine; for it is generating a current directly in opposition to the current which causes it to run. This opposing current serves as a resistance to the current supplied to the motor, and varies with the speed of the motor.

Now, in the Thomson-Houston motor, which is here illustrated, if the speed has a tendency to slacken, this opposing current necessarily becomes less, and thus admits to the motor more of the supplycurrent, which, in its turn, brings back the speed of the motor to its normal speed. The working-power of the motor increases as the square of the current, so that a slight increase in the current (due to the momentary slackening of the speed) is sufficient to make the

horse-power. The larger sizes are, of course, especially valuable for the transmission of power from waterfalls whose distance unfits their utilization by the old methods. Factories may be placed some distance from the water-supply, and get power over the wires.

In addition to the stationary motor, the Thomson-Houston Company have developed extensively those applicable to electric streetcars, having in operation twenty-three electric roads, and eleven in process of construction.

The accompanying illustration represents two Thomson-Houston motors in the exhibition of the Board of Trade at New Bedford, Mass. These motors are supplied by current from the central electric-lighting station of the New Bedford Gas Company, and are furnishing to the shafting all the power required in the various exhibits at this fair.

THE EDISON LIGHT FOR HOUSES, STORES, THEATRES, ETC.

THERE is probably no new industry of equal magnitude that is comparatively so little known to the general public, even in this city, as that of supplying the Edison incandescent light from central stations for interior illumination. Six years ago a small station was started at 255 and 257 Pearl Street. This station has been running continuously, night and day, since Sept. 4. 1882, and is now supplying some 15,000 lamps through a network of 56 miles

About 165 miles of conductors were laid under ground, covering a district from 18th to 59th Streets, and from Sixth to Fourth Avenues; and two substantial buildings were erected, one on 39th Street, near Broadway; and one on 26th Street, near Sixth Avenue. These stations are about completed, and ready to furnish lights, and will have an ultimate capacity of 50,000 lamps each. This great luxury, so long enjoyed by many business-men in their downtown offices, will now be within reach of their uptown homes, and our citizens will welcome a light which does not heat or vitiate the atmosphere by burning up the oxygen; does not destroy or deteriorate decorations, pictures, books, etc.; obviates risk of fire; is as conducive to the preservation of eyesight as the natural light of the sun; and is capable of innumerable applications for ornamental and decorative purposes, as well as for the supplying of power for pumps, elevators, ventilating-fans, sewing-machines. For these and many other purposes the electric current will be ever present, night and day, and will be furnished and charged for by a meter the accuracy of which has been proved by six years of practical use, and at prices that will place one of the greatest luxuries of modern times within reach of all.

[graphic][subsumed]

NEW EDISON CENTRAL STATION, W. 26TH STREET, NEW YORK.

of underground conductors. It was freely predicted that mechanical and electrical difficulties would constitute a barrier to its success; but, these apparently insurmountable obstacles having been overcome by the indomitable perseverance and peerless skill of Mr. Edison, the next prognostication was financial failure. In spite of these dire forebodings, the enterprise was long ago established upon a successful paying commercial basis, as a result of which the capitalists who were pioneers in the business have recently supplied the capital with which to construct two immense stations for supplying residences, stores, theatres, hotels, etc., in the upper portion of the city.

HADFIELD'S MANGANESE STEEL.'

THE most notable contribution to the metallurgy of manganese and its alloys made in recent years is the paper read before the Institution of Civil Engineers of Great Britain by Mr. Robert A. Hadfield, of Hadfield's Steel Foundry Company, Sheffield, on Manganese steel, the invention of his father, but which the author of the paper has done so much to perfect. This steel has been described in previous reports, but Mr. Hadfield's paper sets forth so clearly some of the very peculiar properties that manganese in large quantities imparts to steel, that, with his permission, we quote from it at considerable length.

The most noticeable characteristics of the Hadfield manganese steel are its peculiar hardness, combined with great toughness, the effect of water-quenching upon the steel, and its electrical properties.

Peculiar Hardness.

It is difficult to accurately describe its peculiar hardness, because all the specimens are exceedingly hard; in fact, it is scarcely possible to machine any of them on a practical scale, yet such hardness varies considerably in degree, being most intense in the cast material, containing 5 to 6 per cent manganese, which no tool will face or touch. A gradual decrease is noted then, and, when about 10 per cent is reached, the softest condition occurs. Then an increase again takes place, and at 22 per cent it is very hard, still not so much so as in the 5 per cent. After passing 22 per cent, the cause of hardness becomes more complicated, owing to the presence of more carbon, 2 per cent and upwards; in fact, the material begins to partake more of the nature of cast iron, though as to strength, when compared with the latter, specimen No. 225 (carbon, 2 per cent; manganese, 23.5 per cent) had a transverse strength of 34 tons against 10 tons for cast iron.

The 8 to 20 per cent material can be machined, although only with the utmost difficulty, as will be seen from the following example. The test-bar No. 22 B (manganese, 14 per cent), which elongated 44.5 per cent without fracture and had a tensile strength of 67 tons, was put under a double-geared 18-inch drill. Over an hour was occupied in drilling one hole one half-inch in diameter by three-fourths inch deep; and even to do this it was requisite to run at the lowest speed, or the edge of the drill would have given way. During this time fifteen to twenty holes of the same size could have been easily drilled in mild steel. Similar results from specimens sent to different engineering firms in Sheffield and elsewhere confirm this test, yet this specimen could be indented by an ordinary hand-hammer; so that, whilst so hard, it may be said to possess "a special kind of softness." Although, when being turned, it appears harder than chilled iron, its softness is particularly noticeable when testing the material for compression. Specimens of 10per-cent manganese steel 1 inch long by .79 inch in diameter,

1 Extract from a paper on Manganese,' by Joseph D. Weeks, to appear in the forthcoming volume of Mineral Resources of the United States,' published by the United States Geological Survey, edited by Dr. W. T. Day.

« AnteriorContinuar »