84 SCIENCE OF THRESHING. 



do work just as truly as does a man who shovels dirt. 



The more heated the body is, the faster do the 

 molecules vibrate, and the more work can they do, or 

 the more energy they have. 



Temperature is a term used to denote the rate of 

 vibration of the molecules of a heated body. It does 

 not express the quantity of energy which a body has, 

 but it does express the way in which the molecules are 

 vibrating. Thus, a body having a high temperature 

 is said to be hot ; a body having a low temperature is 

 said to be cold. The temperature of a small piece 

 of iron may be very high, yet it does not have as 

 much heat as a large piece which may be of the same 

 temperature. 



Bearing these facts in mind, and especially that 

 heat is but a form of energy, or work, let us see how 

 it is made to do work, such as running a threshing 

 machine. 



A heated body may impart the energy of its 

 moving molecules to an adjacent body, or, commonly 

 speaking, heat it. If the heated fuel in the boiler 

 fire-box communicates its heat, its power to do work, 

 its energy, to the walls of the box and shell of the 

 boiler, the latter may in turn, heat or energize or 

 impart the power to do work, to heat water in the 

 boiler. When you heat water, its temperature rises, 

 that is, its molecules commence to vibrate faster and 

 faster. When the temperature reaches 212 degrees, 

 a change occurs in the vibration of the molecules. 

 Their rate of vibration does not increase, but the 

 length of vibration increases, the molecules tending 



