SCIENCE OF THRESHING. 85 



to move farther apart. This causes the body of 

 water as a whole to expand. Another effect of heat 

 is still further exemplified in the expansion of railroad 

 rails in summer, the expansion of tires for setting, 

 etc. 



In other words, the molecules of a substance which 

 is heated, are just as capable of doing work is an 

 able-bodied man armed with a shovel. 



If heat is applied after water in an open vessel 

 has reached a temperature of 212 degrees, the 

 temperature of the water does not change, but 

 instead, the extra energy imparted has resulted 

 in making the molecules increase their length of 

 vibration as well as their rapidity. The molecules 

 have lost their power of inter-attraction or cohe- 

 sion, and are attempting to fly apart or expand. 

 In other words water at the temperature of 

 212 degrees at atmospheric pressure changes from 

 a liquid to a gas, and this gas, if allowed to 

 expand fully, occupies 1,700 times the volume 

 or space which the water did. This gas is 

 known as steam. This energizing of water or 

 putting its particles or molecules into motion, this 

 generating of steam, is accomplished by heating it. 

 As before said, if then this heat has imparted a power 

 to do work, it is evident that a certain amount of heat 

 must impart a certain ability to overcome resistance, 

 a certain energy, and vice versa, the energy will 

 produce a certain amount of heat. 



If the water is confined so that it cannot expand, 

 as in a boiler, and extra heat be applied, the tempera- 



