164 THE FEEDING OF ANIMALS 



The iron rod might have been heated in another way — 

 by plunging it into burning charcoal. Somehow, when it 

 is deposited in the plant, there becomes stored in l^is 

 carbon, in a way about which we can only theorize, what 

 we may call chemical energy, which, when combustion 

 occurs, is changed into heat or molecular motion. From 

 these phenomena we learn that not only are there several 

 manifestations of energy, but that one manifestation is 

 transferable into another. 



240. Transformatioiis of energy through the use of 

 machinery. — Perhaps another illustration may still fiu*- 

 ther serve oiu- purpose. A small dynamo is being run 

 by a pair of horses working in a tread-power such as is 

 used for threshing grain. The horses are constantly 

 climbing up a moving treadway and thereby communi- 

 cating motion to machinery. The energy thus applied 

 is the result of combustion in the body of the horse. This 

 motion, is, by the dynamo, converted into electricity, 

 which, by passing through the carbon film of an incandes- 

 cent lamp and there meeting resistance, is in part, at 

 least, manifested as heat. We have, then, in a chain, 

 muscular effort, motion of the mass (pulleys and wheels), 

 electricity, and heat, all manifestations of energy and 

 all transferable one into the other. 



241. The horse a machine. — ^This is a fairly good pic- 

 ture of what goes on with the horse himself, externally 

 and internally, in sustaining life and performing labor 

 for his owner. It is now known that through the combus- 

 tion of the carbon compounds of vegetable and animal 

 origin, which serve as nutrients, chemical energy may be 

 transformed into those other forms that are manifested in 

 the activities of living beings, and it is a notable triumph 

 of science to be able to declare with certainty that the 



