THE STEAM-ENGINE. 251 



SECTION IV. 



What Is a ^^^- The Steam-EnginG is a mechanical 

 steara-Engine? coDtrivaiice by which coal, wood, or other 

 fuel, is rendered capable of executing any kind of labor.* 



„ , The substance which furnishes the means of callino; the 



How much me. =" 



chanical force powers of coal into activity is water; two ounces of coal, with 



can be excited a proper arrange'ment will evaporate about one pint of water; 



tioa of two this will produce 216 gallons of steam, which can exert a 



ounces of coal? mgdianical force equivalent to raising a weight of 37 tons to 

 the height of one foot. 



It has been found bv experiment that the greatest amount 

 IIow does the „. ,., ' ^ , .... 



force of a man of force which a man can exert when applying his strength to 



compare with ^-^e bc-st advantage throuarh the help of machinery, is equal to 



erated by the elevating one and a half millions of pounds to the height of 



combustion of ^^g ^^^^ ^y ^Qj-king on a treadmill continuously for eight 



hours. A well-constructed steam-engine will perform the 



same labor with an expenditure of a pound and a half of coaL 



The average power of an able-bodied man during his active 

 How much coal ,.„ . , . x i ^ ^^ .^ ^ ^i . /. 



is equivalent to life, Supposing him to work tor twenty years at the rate of 



the whole ac- eight hours per dav, is represented bv an equivalent of about 

 tive power of ° r . i r . -l 



a man ? four tons of coal, since the consumption of that amount will 



evolve in a steam-engine, fully as much mechanical force. 

 The great pyramid of Egypt is five hundred feet high, and weiglis twelve 

 thousand seven hundred and sixty millions of pounds. Herodotus states that 

 in constructing it one hundred thoiteand men were constantly employed for 

 twenty years. At the present time, with the consumption of 480 tons of 

 coal, all the materials could be raised to their present position from the 

 ground in comparatively little time. 



, . , The greatest work ever known to have been performed by 



What IS the ° . . . , /. 



greatest amount a steam-engine, was to raise sixty thousand tons of water a 



of work evi;r fg^j. jjj„jj ^s^th the expenditure of one bushel of coal. This 

 acconiphshed o i 



by a steam- work was accomplished bj' one of the engines employed m 



engine ? ^-^^ ^^^^ ^f Cornwall, England. 



• "Coals are by It made to spin, weave, dye, print, and dress silks, cottons, woolens, 

 and other cloths; to make paper, and print books upon it when made; to convert com 

 Into flour ; to express oil from the olive, and wine from the grape ; to draw up metals 

 from the bowels of the earth ; to pound and smelt it ; to melt and mold it ; to roll it 

 and fashion it into every desirable form ; to transport these manifold products of its own 

 labor to the doors of those for whose convenience they are produced ; to carry persons and 

 goods over the waters of rivers, lakes, seas, and oceans, in opposition alike to the natural 

 difficulties of wind and water ; to carry the wind-bound ship out of port, to place her on 

 the open deep, ready to commence her voyage ; to transport over the surface of the sea 

 and the land, persons and information from town to town, and from country to country, 

 with a spped as much exceeding the ordinary wind, as the ordinary wind exceeds that of 

 a pedestrian." — Lardner, 



