AGRICULTURAL SUBSTANCES CARRY FORCE 23 



an engine and allowing it to expend its force on the 

 piston, the force, or energy, which was liberated from 

 the fuel by the fire, is transferred to the movement of 

 the engine. In doing this the steam is partially con- 

 densed, or changed again to water the heat has been 

 liberated. The movement or power produced by the 

 steam in the engine may be conducted by means of a 

 belt to a mill or other machinery, or to 

 an electric dynamo, where the force is 

 Figures, common wheat, changed again into another form of 



The average yield of 89 * . 



samples of common Blue energy. 1 his electricity here eren- 



Stem wheat grown in vari- J 



1902 p wa? i?3 M busheTs ta per erate d mav be conducted for miles 

 acre - over wires, turned into an electric 



motor and used as power for various purposes, or it may 

 be made again to give up its energy in the form of heat. 

 This heat may be used to produce steam in another 

 boiler, or to warm houses, or it may be changed to the 

 form of light in an electric lamp and used to illuminate 

 our dwellings and streets. 



The plant, then, is a storage battery in which is stored 

 up, from the sun, energy which may be appropriated for 

 use by animals. Animals having incorporated into their 

 bodies many of these plant storage batteries, usually 

 somewhat changed in composition, they also become 

 reservoirs of energy. If man eats the flesh of an animal 

 and utilizes its force in the form of labor, he is simply 

 drawing upon the supply of 



energy that the plants stored ^^^^^^JM^fe^gg, 

 up from the vast resources of ^*^^^^* 



/ Figure 4. A new wheat originated 



the SUn. by selection. The average yield of 89 



samples of Minnesota No. 169, a newly- 



. , 



Specialized plants and gjj "*> S^ff |gS* 

 animals. Just as the machin- S 

 ist tries to improve the boiler 5 n b w usneis r Tcre n 



t . ,1 1 11 i . 3.3 bushels, or 18 per cent. 



and engine that shall best 



receive and transmit from the fuel the force it liberates 



upon burning, so the farmer seeks the best plants with 



