271 



Madison Co., N. Y., a representation of which is given 

 in the accompanying figure (fig. 292.) When intended to 

 move from place to place, these engines are furnished ready 

 mounted on wheels (fig. 293). The twelve-horse-power 

 engines cost about $1,000, and have thrashed over a hund- 

 red bushels per hour, using half a cord of wood, or 300 

 or 400 lbs. of coal for ten hours. A Western farmer 

 thrashed 14,250 bushels of wheat in five consecutive weeks, 

 Avorking five and a half days each, with one of tljese en- 

 gines. The smoke-pipe is guarded, so that straw placed 

 within a few inches cannot be set on fire. 



More difficulty obviously exists in adapting the steam- 

 engine to plowing than for stationary purposes. In order 

 to possess sufficient power, when used as a locomotive, 

 the engine must be made so heavy as to sink in common 

 soft soil even with large and broad wheels ; and this 

 tendency is increased by the jar of the machinery which 

 these wheels support. For this reason, all locomotive 

 plows have failed. Better success has attended the use 

 of stationary engines, employed for drawing gangs of 

 plows, by means of wire rope, across the fields. In Eng- 

 land, where much of the soil is tenacious, and where fuel 

 and manual labor are cheap, and horse labor expensive, 

 this mode of plowing has been found profitable when em- 

 ployed on an extensive scale, and is now much used. 



EXCEPTION TO EXPANSION BY HEAT. 



A striking exception to the general law of exj^ansion by 

 ;ieat occurs in the freezing of water.* During its change 

 to a solid state, it increases in bulk about one-twelfth, and 

 this expansion is accompanied with great force. The 

 bottoms of barrels are burst out, and cast-iron kettles are 

 split asunder, when water is sufiered wholly to freeze in 



* There are a very few other substauces which expand on passing 

 from a liquid to a solid state. 



