The practical application of the preceding formula will be shown by the following examples.

EXAMPLES.

1. A 36-inch cylinder with 5 feet stroke is supplied by a boiler evaporating effectively 60 cubic feet of water per hour, and the piston makes 20 strokes per minute without expansion ; — what is the power of the engine and the pressure of steam in the cylinder?

Let it be assumed that r = 6 x 144: 864 and m 0.1. Since the engine is a condensing engine, we have b=164 and e'=3691399. By the formulæ (25.) and (26.) we have

and since by the data we have

W = 1 A = 7·069 V= 2n L = 40 x 5.5 the formula, by these substitutions, becomes

220,

Since e 1, the pressure P of steam in the cylinder, by (18.), is

which being the pressure in pounds per square foot, the pressure per square inch will be 15 lbs.

2. To find the effective evaporation necessary to produce a power of 80 horses with the same engine. Also, find the pressure of steam in the cylinder, the speed of the piston being the same.

By the formula (32.), with the above substitutions, we have
33000 × 80 × 1·1 + 220 × 7·069 × 1028
W=
= 1.22.

3691399

The evaporating power would therefore be only increased 22 per cent., while the working power of the engine would be increased nearly 40 per cent.

The pressure P in the cylinder will be given, by (18.), as before. 1.22 × 3691399 2732;

P

1555.18

164 =

3. What must be the diameter of a cylinder to work with a power of a hundred horses, supplied by a boiler evaporating effectively 70 cubic feet of water per hour, the mean speed of the piston being 240 feet per minute, and the steam being cut off at half stroke? Also, what will be the full pressure of steam on the piston?

Taking, as in the former examples, m = 0·1, b = 164, and r = 864, we shall have

H = 100 W=11 V=240,

and by the column for condensing engines, in table, p. 519, we have e' = 6029916, where e = 0·50. Making these substitutions in We 33000 H (1+m) + VA (b + r),

we shall have

=

1 × 6029916 = 3300000 × 1·1 + 240 × 1028 × A. Whence we find

A = 13.8;

and by the table, p. 520, the corresponding diameter of the cylinder will be 50 inches.

If P' be the full pressure of the steam, we shall have, by (18.),

which being in pounds per square foot, the pressure per square inch will be 1610 lbs.

INDEX.

Air, elasticity of, 28. May be partially expelled from a vessel by the
application of heat, 44.

America, steam navigation first established in, 487. Circumstances
which led to it, 488. Fitch and Rumsey, their attempts to apply
the single-acting engine to the propulsion of vessels, 489. Stevens
of Hoboken commences experiments on steam navigation, 489.
Experiments of Livingstone and Fulton, 489. Fulton's first boat,
490. The Hudson navigated by steam, 491. Extension and im-
provement of river navigation, 492. American steamers, 494. Dif-
ference between them and European steamers, 494. Steamers on
the Hudson, 494. American paddle-wheels, 495. Sea-going Ame-
rican steamers, 496. Speed attained by American steamers, 497.
Lake steamers, 499. The Mississippi and its tributaries, 499.
Steam-boats navigating it, 500. Their structure and machinery,
500. New Orleans Harbour, 503. Steam tugs, 503.
Atmosphere, 38. Weight of, 39.

Atmospheric air, mechanical properties of, 38. Composition of, 253.
Atmospheric engine, Thomas Newcomen the reputed inventor of, 62.
Description of, as first constructed by Newcomen, 67. The opera-
tion of considered, 69. Not unfrequently used in preference to the
modern steam engine, 72. Advantages which it possessed over Sa-
very's, 73. Considerably improved by Beighton, 75. John Smeaton
investigates this machine, 76. Brindley obtains a patent for im-
provements in, 76. Applied by Champion of Bristol to raise water,
181. Possessed but limited power of adaptation to a varying load,
151. Expedient to remedy this, 151. Working-beam, cylinder, and
piston applied to by Newcomen, 322.

Atmospheric pressure rendered available as a mechanic agent by Denis
Papin, 38. Means of measuring the force of, 39. The idea of
using against a vacuum or partial vacuum to work a piston in a cylin-
der, suggested by Otto Guericke, 73.

Barometer gauge, 272.

Barton's piston, 248.

Beighton, his improvement of the atmospheric engine, 75.

Black, Dr., his doctrine of latent heat, 93.

Blasco de Garay, his contrivance to propel vessels, 16. The contrivance
of, probably identical with that of Hero, 17.

Blinkensop, his locomotive engine, 337.

Blowing-box, 429.

Blowing out, Seaward's method of, 454.

Boiler, forms of, most convenient, 255. The waggon boiler adopted by
Watt, 255. Furnace, 256. Method of feeding, 257. Combustion
of gas in flues, 260. Mr. Williams's method of consuming the un-
burned gases which escape from the grate, and are carried through
the flues, 260. Construction of grate and ash-pit, 261. Magnitude
of heating surface of boiler, 262. Capacity of, must be proportioned
to the quantity of water to be evaporated, 263. Water-space and
steam-space in boiler, 263. Proportion of water-space in the boiler,
how to be regulated, 264. Position of flues, 264. Method of feed-
ing, 265. The magnitude of the feed should be equal to the quan-
tity of water evaporated, 265. Different methods for indicating the
level of the water in the boiler, 266. Level guages, 266. Self-
regulating feeder, 267. Another method of arranging, 269. Steam
gauge, 270. Thermometer gauge, 271. Barometer gauge, 272. The
indicator to measure the mean efficient force of the piston invented by
Watt, 274. The counter contrived by Watt, 278. Safety valve, 279.
Fusible plugs used in high pressure boilers, 280. Self-regulating
damper, 281. Self-regulating furnace invented by Brunton, 283.
Duty of a boiler, 294. Boilers of locomotive engines, 351. Con-
struction of the boiler of Gurney's steam carriage, 423. All boilers
require occasional cleansing, 427. Gurney's method of removing
crust of deposited matter in boilers, 427. The boiler of Dr. Church's
engine formed of copper, 439. Boilers in marine engines, 449.
Effects of sea-water in, 450. Remedies for them, 451. Substitution
of copper for iron, 460. Expedient of coating boilers with felt, ap-

plied by Watt, 463.

Booth, Mr., his report on locomotive engines, 361.

Boulton and Watt's experiments on the horse power of engines, 288.
Branca, Giovanni, his machine for propelling a wheel by a blast of
steam, 22.

Brindley (James) obtains a patent for improvements in atmospheric
engine, 76. Undertook to erect an engine at Newcastle-under-Lyne,
76. Discouraged by the obstacles thrown in his way, 76.
Brougham, Lord, his sketch of Watt's character, 313. Inscription from
the pen of, on Watt's monument in Westminster Abbey, 320.
Buffers, 404.

Cartwright's engine to use the vapour of alcohol to work the piston, 245.
His piston, 247.

Cawley and Newcomen obtain a patent for the atmospheric engine,
64.

Champion applies atmospheric engine to raise water, 181.

Chapman, Messrs., their locomotive engine, 337.

Chlorine introduced in bleaching by Watt, 310.

Church, Dr., his steam engine, 439. The boiler formed of copper,
439.

Coals, the virtues and powers which steam has conferred upon, 6. The
amount of labour a bushel of performs by means of the steam en-
gine, compared with horse power, 7. Constituents of, 252. Process
of combustion, 252.

Coal mines, apprehensions as to the possibility of the exhaustion of

groundless, 8.

Cocks, friction on, 240.

Cocks and valves, 227.

Combustion of gas in flues, 260.

Condensation by injection, accidental discovery of, 69.

Condensation in the cylinder incompatible with a due economy of fuel,
120.

Condensing principle, circumstance which led to Savery's discovery of,
47.

Condensing pipe in Savery's engine, 52.

Condensing out of the cylinder, 120.

Condensing jet, 191.

Conical steam valves, 228.

Conversion of ice into water, 103. Of water into steam, 105.

Copying press invented by Watt, 302.

Cornish system of inspection, 297.

Cornish engines, improvement of, 298.

of, 299.

Historical detail of the duty

Cylinders, Wilkinson's machine for accurately boring the insides of,
149.

D valve, 230.

Dalton and Gay-Lussac, law of, relating to the pressure of elastic
bodies, 171.

Dixon, Mr. The substitution of brass for copper tubes in locomotive
engines ascribed to him, 370.

Double clack-valve, 228.

Eccentric, 225. Two expedients to reverse the position of, 379.
Effect of an engine, 285.

Elastic fluids. The law according to which the pressure of, increases
with their temperature, discovered by Dalton and Gay-Lussac, 171.
Evaporation of water and other liquids, physical and mechanical prin-
ciples connected with, 97.

Expansion of common steam, effects of, 173.

Expansive action of steam, 159. Stated by Watt in a letter to Dr.
Small, 157. Its principle explained, 158. Mechanical effect result-
ing from it, 161. Computed effect of cutting off steam at different
portions of the stroke, 162. Involves the condition of a variation in
the intensity of the moving power, 163. Expedients for equalising
the power, 164. The expansive principle in the engines constructed
by Boulton and Watt, limited, 165. Its more extensive application
in the Cornish engines, 165. Methods of equalising, 174. Descrip-
tion of Hornblower's engine for this purpose, 174.

Expansive principle, application of in marine engines, 466.

Farey on the steam engine, quotation from, relative to Savery's engine,
58. His evidence before the House of Commons, 435.