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ENGINEERING MAGAZINE,

COMMENCED JANUARY, 1869,

Published on the 15th of the month at $5.00 per year.

The January number of this MAGAZINE, for the year 1881, begins the Twenty-fourth Volume. Beginning as an Eclectic Journal, and presenting almost exclusively matter selected from current literature, it has gradually become the chief medium through which the leading writers on engineering subjects can best present their original essays to American readers.

The attitude of the MAGAZINE has been, and will continue to be, that of a journal of original and selected papers upon subjects relating to modern advanced Engineering. Theoretical and Practical Essays are alike presented in its pages, although the latter largely out-number the former, as best suited to the tastes and demands of the American Engineers. Some of the most valuable contributions to the literature of technical science within the last few years have been first presented in these pages.

Among the more extended original contributions to the later volumes may be cited new contributions to Graphical Statics-- Transmission of Power by Wire Ropes-Maximum Stresses in Framed Bridges-- Momentum and Vis Viva—Rapid Methods of Laying out Gearing-Transmission of Power by Compressed Air–Geographica. SurveyingMathematical Theory of Fluid Motion - Thermodynamics - Practical Theory of Voussoir Arches--Cable Making for Suspension Bridges, &c., &c.

To the above may be added the following valuable essays, translated from foreign sources, which have first appeared in these pages: Linkages and their ApplicationsThe Origin of Metallurgy--and The Theory of Ice Machines.

The plans for future volumes comprehend many improvements in the same direction. The wants of the educated practical engineer, who desires to keep in the foremost rank of his profession will be steadily kept in view, and our constantly increasing resources for supplying the best of scientific information will be employed to secure such result.

Cloth covers for Volumes I. to XXIII. inclusive, elegantly stamped in gilt, will be furnished by the publisher, for fifty cents each.

If the back numbers be sent, the volumes will be bound neatly in black cloth and lettered, for seventy-five cents each. The expense of carriage must be borne by the subscriber.

Notice to New Subscribers.- Persons commencing their subscriptions with the Twenty-fourth Volume (January, 1881), and who are desirous of possessing the work from its com. mencement, will be supplied with Volumes I, to XXIII. inclusive, neatly bound in cloth, for $60.00, in half morocco, $90.00.

Notice to Clubs.-An extra copy will be supplied gratis to every Club of Five subscribers at $5.00 each, sent in one remittance.

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CONTENTS.

PAGE.

SMALL MOTIVE POWER. By Henry S. H. Shaw, Stud. Inst.
C.E. 1. (Illustrated). ....

Fron Selected Papers Inst. Civil Eng... 261 PNEUMATIC PROPELLER FOR RAILWAYS. By L. Gonin....From Abstracts of Inst. Civil Eng....

279 NOTES ON RAILROADING. By J. A. L. Waddell, C.E. (Illustrated)...

From Papers of the Pi Eta Society.... 281 SANITARY ADMINISTRATION IN PARIS..

Architect..

296 THE RELATION BETWEEN ELECTRICITY AND LIGHT. Nature....

299 SCIENCE TEACHING IN THE PUBLIC SCHOOLS.....

Proc. Am. A8800. Adrancement of Science. 303 On Dust, Fors, AND CLOUDs. By John Aitken... Nature....

308 ON THE CAUSE OF CAVITIES IN CAST STEEL. By Dr. F. C. G. Muller, of Brandenburg...

. Trans. from Glaser's Annalen .... 311 THE GEOMETRICAL INTERPRETATION OF IMAGINARY QUAN

TITIES. Translated from the French of M. Argand by
Prof. A. S. Hardy. IV. (Illustrated)...

.Contrib. to Van Nostrands Magazine.. 313 ON THE CALCULATION OF DIMENSIONS AS DEPENDING ON

THE ULTIMATE WORKING STRENGTH OF MATERIALS.... Trans. by George Rudolph Bodner.... THE AMOUNT OF RAINFALL IN ITS RELATION TO THE WATER SUPPLY OF A City. By Julius W. Adams....

Written for Van Nostrand's Magazine. 336 ON THE VARIOUS MODES OF TRANSMISSION OF POWER TO A DISTANCE. By M. A. Achard ......

Paper read before Inst. Mech. Eng..... 339

PARAGRAPHS.-Note on the Present System of Permanent Way on the Six Chief Railways of France; Electric Prop

erties of Paper, 280. Rousset's Deep Sea Sounder, 324,

REPORTS OF ENGINEERING SOCIETIES.-American Society of Civil Engineers, 343; Boston Society of

Civil Engineers; Polytechnic Club of the American Institute, 344.

ENGINEERING NOTES.-On a Rope Tramway at Strasburg ; Swiss Triangulation; The Suez Canal Tonnage, 346.

IRON AND STEEL NOTES.- A Great Crucible Steel Casting, 346 ; Bessemer Steel in the United States ; Chemical

Society on Bar Iron, 347. RAILWAY NOTES.- Massachusetts Railroads; The Prussian Railway System; European Railway Commission, 347;

Railways and Canals in Canada ; French Railways, 348.

ORDNANCE AND NAVAL.-An Hydraulic Ship: The Austrian Ironclad “ Teget hoff," 348; The New Forty-three

Ton Breech-Loading Gun, 349.

BOOK NOTICES.- Publications Received ; Locomotive Engineering and the Mechanism of Railways, by Zerah Col

burn, 349; Caoutchouc: Gutta Percha et Gomme Factice; Nouveau Traite de Chimie Industrielle, Wagner et L. Gautier; Life History of Our Planet, by Wm. D. Gunning : Easy Lessons in Sanitary Science, by Joseph Wilson, M. D. ; Materials and Construction, by Francis Campin, C. E.; The Steam Engine and its Inventors, by Robert L. Galloway; The Marine Mammals of the N. W. Coast of North America, by Charles M. Scammon ; Sewing Machinery, by J. W. l'rquhart, C.E., 330.

MISCELLANEOUS.-Waterproof Paper-- How Made, 350 ; Freight on Bycycles in England : Diurnal Variations of

the Barometer; Circulation of Air in the St. Gothard Tunnel ; Trade-marks Law in Switzerland ; Color Relations of Metals, 351; Japanese Leather Paper; A Phosphor-Bronze Steam Launch ; German Coal-owners ring, 352.

VAN NOSTRAND'S

ENGINEERING MAGAZINE .

NO. CXLVIII.—APRIL, 1881.–VOL. XXIV.

SMALL MOTIVE POWER.

By HENRY S. H. SHAW, Stud. Inst. C.E.

From Selected Papers of the Institution of Civil Engineers.

I. The introduction of small motors has | ence, the difficulty of assigning an exact been very extensive of late years, and is numerical limit exists, such a limit being still increasing. The object of this pa. after all quite arbitrary; for instance, a per is to consider, in a brief but sys- very small engine, driven at a consideratematic manner, the present state of the ble velocity by high-pressure steam, subject in this country, in order that a might develop as much power as an orcomparison may be formed of the rela- dinary water wheel, or a much larger tive advantages of the various agents engine, under different conditions; but now in use. In order to do this at all though the term in question would insatisfactorily, an outline, at least, must clude the first, it would commonly be be given of the modes of applying these held to exclude the two last; therefore, agents for the purpose, and also the uses it will be interpreted as generally reto which the motors themselves are put; ceived by engineers, and will be taken to so that, after a few preliminary defini- exclude locomotives and marine engines, tions and remarks, the following method factory and mill motors, but to embrace has been adopted:

the large number of engines for what (I.) The working agents are classified, may be called auxiliary purposes, which and the causes of loss by the transfor. are being made more and more to supermation of energy on a small scale are sede muscular energy. briefly considered.

The only direct sources of power at (II.) The agents are taken in order, present used for small motors are fuel and the types of apparatus for applying and a natural head of water, fuel includthem are dealt with and classified, and ing every kind of substance which by their efficiency examined.

chemical action, rapid or slow, develops (III.) Finally, the relative advantages kinetic or actual energy. No source of of the agents are considered, with refer- power can be utilized without some loss ence to the various objects for which of energy, and the “efficiency” of the they are applied.

apparatus used is the exact numerical It is difficult to define exactly what is value of the ratio of the useful work meant by Small Motive Power. Wheth- produced by it, to the energy expended er the size of the motor, the work per- upon it, by means of the working subformed in a given time, or the object for stance or agent; this quantity is, therewhich it is applied be taken for refer- fore, always some fraction less than

VOL. XXIV.No. 4–19.

unity. Before the final application of the action of heat is caused to expand energy takes place, it may undergo a the agent, and thus to do work. Those number of transformations by means of marked (a) (a), (a) may be regarded as various agents, two or more being often merely transmitters of energy, and actemployed in the case of small motors – ing in the secondary way already referas, for instance, when steam power is red to. The respective efficiencies, of two used to produce an artificial "head of of these, and also of steam, for this purwater or a current of electricity, which pose, have been dealt with in a paper by latter may produce work; but since the Mr. Robinson,* M. Inst. c. E., from resultant efficiency is the product of the which paper it appears that water stands fractions representing that of each in the highest, but the loss of head, varytermediate piece of apparatus, the final ing inversely as the fifth power of the advantage io be gained must be bal- diameter of the transmitting pipe would anced against the loss necessarily en cause its utility to diminish rapidly with tailed by the use of each extra agent.

the size of the motor. It is only reThe same source of power may be ap- cently that electricity has been much plied to impart energy to motors by thought of for this purpose, or at any various agents and in different ways, rate has been practically applied, and and in order to avoid confusion, in stat- that agent is treated in Section II. aling the efficiency of an agent, the source most entirely with reference to this obof power should also be stated; thus, ject. taking gas as the source of power in the Before proceeding to examine the effigas engine, and coal in the steam engine, ciencies of the agents separately, it will the result of comparing these agents is be well to point out the losses of differvery different to that obtained by taking ent kinds attending the transformation coal as the source in both cases, and in- of energy, which are common to all. troducing as a factor in the former case These take place, the efficiency of the gas-making appara (1.) In dissipation, caused by the tus.

tendency of the agent to lose the energy The extent to which an agent is to be imparted to it by communicating it to used may have much to do with determ- surrounding bodies, as, for instance, by ining its suitability for any purpose, and conduction and radiation in the case of may considerably modify its application; heat, and by leakage with a head of indeed, the choice of the agent may de water. pend on very different considerations, (2.) In the necessary rejection of en. according as it is to be used on a large ergy due to the conditions of working. or a small scale. The importance of this

(3.) In the mechanical arrangements, will be shown hereafter, and leads to the in connection with which there are two agents applicable for use with small mo- principal losses, the one by friction, tors being more numerous than with which is unavoidable, but may be relarge ones.

duced to a minimum by judicious design,

the other by an improper supply of the Section 1.

agent, which supply may be either in

sufficient or excessive; in the former (1.) The agents may be thus classified:

case the friction of the working parts Steam

absorbs an increasing proportion of the I Coal Gas Petroleum, &c, Heat engines.

energy expended; in the latter the reAir | Heated

locity of the motor increases, until the Compressed

(a, resistances, both useful and prejudicial, Water | Natural head

are equal to the power applied to over7 Artificial bead

come them. | By direct chemical action Electricity By dynamo-electric machine . (a) most important among small motors, the

As already stated, beat engines are The agents classed under “heat en- use of gas and 'hot air being almost engines” form the most important portion, tirely applied to operations on a small and will be, to a certain extent, treated scale; therefore, it seems appropriate to of together, a heat engine being re

* Vide Minutes of Proceedings Inst. C.E., vol. xlix., gailed simply as an apparatus by which

(a)

p. 1.

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