cylinder walls, etc. For example: the amount of heat supplied to the engine in a given time is represented by the number of pounds of steam supplied multiplied by the total heat of one pound of steam. A portion of this heat is used in the jacket, if one be employed, and the remainder passes through the cylinder. The heat entering the jacket is lost partly by radiation from the outside surface, and the remainder enters the walls of the cylinder and is absorbed by the steam within it. The cycle of operations within the cylinder consists of the following phases: (1) A portion of the entering heat is transferred into a small portion of the thickness of the cylinder walls, and heats them to the temperature of the entering steam. This transference of heat is more active during the period of admission and up to the point of cut-off than during any other part of the cycle. (2) Beyond the point of cut-off, the transference of heat continues until the lower pressure due to expansion causes the temperature of the steam to fall below that of the interior surfaces of the cylinder last uncovered. At this point the interchange of heat is reversed, the metal giving up heat to the steam, and causing the re-evaporation of the particles of water condensed on the surface of the cylinder walls and piston. The radiation of heat from the small thicknesses of the interior walls, which were heated during admission to the temperature of the entering steam, commences after cut-off or after the pressure begins to lower by expansion, and continues to the end of the stroke.

A portion of the heat is also expended in the performance of work, and a loss of heat is sustained by radiation from those portions of the cylinder not protected by the jacket. The amount of heat remaining after the steam has passed through these operations is that which is rejected by it through the exhaust valve to the atmosphere or to the condenser.

In the case of an internal combustion engine, the total heat of combustion expended in the working of the engine may be divided into three parts: (1) Heat converted into work and represented by indicated or brake horse power. (2) Heat carried away by the cooling water circulated through the water jacket. (3) The heat lost in the exhaust gases, and through incomplete combustion and radiation.

or

15. Heat Converted into Indicated Brake Horse Power.- The number of footpounds of work done by one pound or one cubic foot of fuel divided by 778, the mechanical equivalent of one British Thermal Unit, will give the number of heat units desired.

16. Heat Carried Away by the Jacket Water. This is determined by measuring the quantity of cooling water passed through the water jacket equivalent to one pound or one cubic foot of fuel consumed, and calculating the amount of heat rejected by multiplying that quantity by the difference of the temperature of the water entering and leaving the jacket.

17. Heat Rejected in the Exhaust Gases, or Total Heat Unused.-The sum of the heat converted into brake horse power and the heat carried away by the jacket water, subtracted from the total heat supplied, will give the total heat rejected or unused.

In order to determine the cost of each horse

and p' height of barometer + (0.073 X reading of manometer); and t-temperature of gas at meter+461.

For example: Assume the heights of the barometer as 29.40 inches; the reading of the manometer as 6 inches; the temperature of the gas 80° F.; and the volume of the gas registered by the meter 350 cubic feet; then for determining (v) the equivalent volume of gas for standard conditions:

p1=29.40+(0.073× 6) =29.84
180+461=541;

20. Total B.T.U.'s Per Hour.- The total amount of gas consumed, in cubic feet, multiplied by its calorific value.

B.T.U's Per Brake Horse Power Hour.The total B.T.U.'s per hour dvided by the brake horse power.

B.T.U.'s Per Indicated Horse-power Hour. - The total B.T.U.'s per hour divided by the indicated horse power.

Friction Horse Power.- The difference between the indicated horse power and the brake horse power.

Thermal Efficiency. The ratio of 2,545 B.T.U.'s to the B.T.U.'s per horse-power hour. Mechanical Efficiency.- The ratio of the brake horse power to the indicated horse power. WILLIAM MOREY, JR., Č.E., Consulting Civil and Mechanical Engineer, New York.

ENGINE INDUSTRY. Notwithstanding the wonderfully rapid development of water power and of the internal combustion engine, the steam engine holds its own in the industries of the world. The total steam engine horse power used in manufacturing in the United States, which was 8,139,574 in 1900, rose to 14,199,339 in the 1910 census. Seven great industries utilize 56 per cent of the horse power employed in manufacturing in this country, and 76 per cent of the power they use is based on the steam engine. The industries meant are lumber, steel works and rolling mills, paper and pulp mills, cotton factories, blast furnaces, foundries and machine shops and grist mills. In only one of the seven- the paper and pulp industry, which requires large quantities of water for dissolving pulp is steam power less used than water power. The fourteen million horse power quoted does not by any means represent the total employment of steam engine power in the country, but only such as the census gathers as reported by manufacturers. It does not cover steam engine power used on vessels, nor used in mines and quarries, nor its vast employment in the locomotives that do most of the haulage on the railways, nor a number of minor uses. These are reported in other ways, or escape enumeration. The best way of measuring the steam engine industry is to note that 450,000 000 long tons of coal are used in the United States every year, and it is estimated that at least 350,000,000 tons of this is consumed under boilers to make steam. Evidently while the coal holds out the steam engine is going to continue the favorite power-producer, because it can be located anywhere and its cost is moderate. Even the electric railway lines around New York city and the electric light and power companies there, hase their power entirely on the steam engine.

There are no complete figures of the engine industry because it is so completely interwoven

with other activities that it cannot be separated. Thousands of machinery manufacturers build steam engines, which are part of this or that special industry, often being for their own use. The internal combustion engines alone are mixed with 20 different industries from up automobiles to blast furnaces and a vast number of engines are built direct-connected to dynamos and credited to the electrical industries. See INTERNAL COMBUSTION ENGINE; GAS ENGINE; STEAM AND STEAM ENGINES; LOCOMOTIVE; LOCOMOTIVE INDUSTRY; AUTOMOBILE ENGINE; AEROPLANE.

ENGINE STARTERS, or “self-starters," auxiliary devices for the purpose of starting gasoline automobiles (or other) engines without laborious method of turning the hand crank commonly provided. Self-starters operate upon either of two principles: the crank shaft is rotated by external mechanism, causing the pistons to charge the cylinders with gas to be exploded when the spark is turned on; or the injection of gas into one or more cylinders without rotation of the crank and the production of a spark in all the cylinders simultaneously so that the charged cylinder will come into action. Mechanical starters are operated by a heavy spring, by compressed air, or by electricity. They require a considerable addition to the machinery of the car as well as to its weight, especially in the case of the electric starter and add many sources of possible trouble in an already complicated machine.

The gas injector system adds simply a small hand pump at the driver's seat or on the dashboard, two strokes of which effects the charging of the cylinders; and the throwing of a switch fires the charge. In automobiles which employ acetylene gas for lighting, an attachment is furnished by which this gas may be used in priming the cylinders for starting. The acetylene mixture is claimed to be more certain of explosion than an uncompressed charge of gasoline vapor and air. Consult Cross, H. H. U., Electric Lighting and Starting) (London 1915); Duryea, C. E. and Homans, J. E., 'The Automobile Book' (New York 1916); Pagé, V. W., The Modern Gasoline Automobile' (New York 1912).

ENGINEER CORPS, a branch of the service of the United States Navy; and of those of other countries. The first step toward the organization of an engineer corps in the United States Navy was taken on 2 July 1836, when C. H. Haswell (q.v.) was appointed chief engineer of the Fulton; it was not, however, until 31 Aug. 1842 that Congress passed an act providing for a regular corps, under which act chief engineers were "commissioned" and assistants "warranted." On 3 March 1845 Congress passed an act whereby the power of appointing engineer officers was transferred from the Secretary of the Navy to the President "by and with the advice and consent of the Senate." With the growth of the Navy the corps gradually increased till at the time of the Civil War there were 474 regulars and 1.803 volunteers.

A course of instruction for cadet engineers was established at the Naval Academy by act of Congress 4 July 1864. The original two-year course was changed to four years in 1874 and continued in vogue till 1882, when on 5 August Congress amalgamated the cadet engineers and

midshipmen and they are now known as naval cadets. The cadets then took the usual six years' course at the Academy and upon completion of the third year of the course were divided into an Engineer Division and a Line Division in proportion to the vacancies that have occurred in the several corps during the preceding year. At the end of the six years' course appointments to fill vacancies in the Line and in the Marine Corps were made from the Line Division, and to fill vacancies in the Engineer Corps from the Engineer Division. If, after making assignments as above, there should still be vacancies in one branch and surplus graduates in the other, the vacancies in the former were filled by assignment to it of surplus graduates from the latter. This arrangement was in vogue until the Line and Engineer Corps were amalgamated under the act of 3 March 1899, at which time the Engineer Corps ceased to be a separate organization, the older officers now being required to perform engineering duties only, whereas the younger officers must pass examinations in navigation, gunnery, seamanship, etc. A grade of warrant machinists to perform watch duties was also established because of the lack of commissioned officers for this work. See NAVAL ACADEMY, UNITED STATES; UNITED STATES NAVY.

ENGINEERING is, in its strict sense, the art of designing, constructing, or using engines, but the word is now applied in a more extended sense, not only to that art, but to that of executing such works as are the objects of civil and military architecture, in which engines or other mechanical appliances are extensively employed. Engineering is divided into many branches, the more important being civil, mechanical, electrical, mining, military, marine and sanitary engineering.

Among the most notable of the engineering works belonging to very remote antiquity are the pyramids of Egypt. The rude stone monuments of the north, as at Stonehenge and Carnac, also testify to some engineering skill. The harbors and temples of ancient Greece are very memorable. The buildings of ancient Rome - its theatres, temples, baths and aqueducts, its roads, bridges and drainage-works-vie in extent and magnificence with the most celebrated works of modern times. From that period down to the commencement of the 18th century, the most extensive works executed were the canals, embankments and other hydraulic construction used by the Dutch for the purposes of inland navigation and to protect their low lands from the sea; the canals of North Italy; and the cathedrals and fortifications of mediæval Europe.

If the question were asked as to the characteristic feature of the modern applied science of engineering, the reply would undoubtedly be: "The wholesale manner in which work is carried on." It is not so very long ago that everything except the smallest articles and those required in great quantity were made singly, or at least in small lots; and even when standardizing and interchangeability were introduced these methods were by no means used in a way which showed a realization of their possibilities. The present tendency, on the contrary, is toward the elimination altogether of things which cannot be made wholesale; and methods which formerly applied

to firearms, sewing-machines, typewriters and the like are now in general use in the manufacture of steam engines, machine tools, electrical machinery and nearly all mechanical products.

This has been brought about by a combination of two processes: (1) the standardization of methods of manufacture; and (2) the discouragement of the demand for special articles. Formerly the customer told the manufacturer what was wanted and the latter hastened to produce it. Or the plans and specifications for a certain structure were prepared by a consulting engineer and all bidders were required to conform to these documents in the minutest details; no two such specifications being alike. At the present time the customer, knowing what he wishes to accomplish, seeks to do so as best he may by means of the standard articles in the market; or if it be a great engineering structure, the engineer specifies only the general requirements to be met, leaving each manufacturer to meet these with his own standardized product. The influence of these modifications in engineering practice extends to the manufacture and supply of materials.

The result of this concentration and standardization has been to reduce costs very materially and render possible undertakings which would otherwise be prohibitory in price. While to a certain extent it has obliterated individuality in design, it has also removed much useless repetition and has prevented needless expense in the production of rival machines, differing but slightly in design, yet requiring duplications of drawings, patterns and tools. There is little doubt that it is to this wholesale development of various departments of engineering work that the rapid extension of the share of the United States in the work of the world is largely due. See CIVIL ENGINEERING; ELECTRICAL ENGINEERING; HYDRAULIC ENGINEERING; MECHANICAL ENGINEERING; ENGINEERING, MARINE; FORTIFICATIONS; MINING ENGINEERING; NAVAL CONSTRUCTION; SANITARY ENGINEERING. Also ENGINEERING TERMS; ENGINEERING INSTRUMENTS; EDUCATION, ENGINEERING; MECHANICS.

ENGINEERING, Electrical. See ELECTRICAL ENGINEERING.

ENGINEERING, Hydraulic. See HyDRAULIC ENGINEERING.

ENGINEERING, Marine, is partly military and partly civil, embracing naval architecture, building and operating of ships and naval accessories. In the military sense, it comprises the construction of war vessels and the construction and placing of torpedoes, submarine mines, etc. See NAVY; NAVAL CONSTRUCTION; SUBMARINE MINES, etc.

ENGINEERING, Mechanical. See MECHANICAL ENGINEERING.

ENGINEERING, Mining. See MINING

ENGINEERING.

divided demands so many special appliances for their requirements that no one description is possible and an extended catalogue is inadmissible within the limits of this article. The earliest known engineering instrument was the Diopter of Hero of Alexandria, 130 B.C., although rude appliances must have been used long before that time by the ancient engineers in the construction of the public works of Chaldæa and Egypt, the ruins of which even now awaken our admiration and wonder. was not, however, until the beginning of the 19th century that the great impulse to the construction and use of engineers' instruments was

It

and

to

lightness of construction combined with great strength and an adaptability of parts for the special service required. It is not the purpose of this article attempt a description of the various instruments used by engineers - this may be found in the article SURVEYING- but to give the reader a general idea of their construction.

The metals used in the construction of engineers' instruments are principally the alloys of copper and tin with small quantities of silver, aluminum and German silver. Great care must be constantly exercised that these substances be free from iron or other materials which would

given by the advance of civilization and commerce incident to the application of steam as a motive power on sea and land. Since that time great advances have been made not only in the design and accuracy of engineering instruments but also in the invention of new instruments for the many purposes required by engineers in the construction of railroads, canals, bridges, harbors, etc.

The characteristics of engineers' instruments differ in the various nations as the requirements of engineering practice and thus American engineers' instruments possess a distinct character of their Own as compared with other nations, having as a rule few parts

affect the magnetic needle. In the construction of an instrument such a distribution of the metals is aimed at that the greatest strength consistent with light weight may be obtained and that the metals coming into contact at the bearing surface may be of such varying composition as to cause the least friction.

Take, for the purpose of better illustration, an American transit, illustrated herewith, as typical, as far as the construction is concerned, of nearly all engineering instruments. The plate of the instrument on which the magnetic needle is mounted, or as it is termed, the compass circle, is turned with great care so that the surface may be absolutely true and is gradu

ated usually into 720 spaces, each representing one-half of a degree.

Compass circles are usually figured in quadrants of a circle, that is, from 0 at the point marked "N" or "North" to 90 and back again, while the figuring of the limb varies with the custom of the maker or the requirements of the engineer.

In engineers' instruments, however, the angular measurements are made usually without the use of the needle, by a telescope so mounted as to revolve in a vertical or a horizontal plane. The angular measurement of its movement is indicated on circles divided into fractional spaces of a degree and read for convenience to finer spaces by one or more verniers. Accuracy of graduation of the compass circle, and especially of the limb, is essential to the perfection of the instrument, and great pains are taken by manufacturers in perfecting and improving engines for graduating. The best machines are automatic in action and the spaces are so accurately laid off that there is no appreciable error in the finished work. The instrument rests on the socket or bearing surface to which the compass plate and limb are

rays of light entering the object glass may be properly refracted and concentrated at a point I called the focus.

The making of the lenses is an operation requiring much skill in manufacture, as upon the accurate grinding of the curved surfaces depends the quality of the telescope.

At the focus of the object glass are placed the cross-wires, which are filaments of spider web or very fine platinum. In conjunction with these are often used two more wires commonly called stadia wires, so placed that they intercept on a rod a space proportional to its distance from the instrument, thus furnishing an efficient method of ascertaining distances directly by the observer. The metal parts of the instrument, having been prepared, are polished with some suitable material, a preparation of rouge being generally used for finishing the surface of the screws, and the larger surfaces being finished with fine emery paper. The larger parts are usually colored dark to avoid reflection of the sun, while the smaller ones, such as screws, etc., are left bright in order that there may be a pleasing contrast between the different parts of the instrument. The

attached; the surfaces of the socket must be so accurately fitted together as to produce no error when the parts are moved on each other. The socket is mounted on a leveling head, which is actuated by three, or in the usual American practice, by four leveling screws, as shown, by means of which the instrument can be accurately leveled. Upon the compass plate are placed the standards which support the telescope, the preparation of the optical parts of which is next in importance to the fitting of the socket and the graduation.

The telescope consists of an eye piece and object glass mounted in a tube. The eye piece is simply a magnifier of the image produced at the focus of the object glass. Two kinds of eye pieces are used, one showing the image erect, and the other showing the image inverted. The object glass is composed of two plates of optical glass of such specific gravity and refractive index that it will magnify the image clearly without prismatic colors. To secure achromatism the two parts of the object lens are made the one of crown and the other of flint glass, the crown being a light glass of soda and silica and the flint being a heavier glass containing potash and lead. The surfaces of each are curved to such a degree that the

parts, prepared as above, are covered with a thin coat of lacquer, a preparation of shellac and alcohol, applied after heating. All the parts are assembled and fitted together, and the instrument is then ready for the final complete adjustment. This consists in fitting the sockets so that they will move freely on each other, placing the compass plate and limb in position on the sockets, making the limb truly concentric with the socket and placing the verniers in position. The telescope must be so adjusted that its parts may work freely, and having been supplied with optical parts, etc., it is then fitted to the standards or supports previously placed in position on the compass circle. The whole instrument is then tested for accuracy and if found correct is packed in its case and is ready for use.

The above description is only intended to give a general idea of the construction of a typical instrument, but the same methods will practically apply in the construction of all engineering instruments, such as levels, plane-tables, alidades, and the various kinds of compasses,

etc.

ENGINEERING SCHOOL. See EDUCATION, TECHNICAL.