102 SCIENCE OF THRESHING. 



Column 6 gives the SPECIFIC VOLUME of a pound 

 of steam at the given temperature or pressure, which 

 is expressed in pounds, being the weight of a cubic 

 foot of steam at the pressure given. 



Column 7 gives the number of cubic feet occupied 

 by one pound of steam at the given temperature, or 



its SPECIFIC VOLUME. 



Column 8 gives the ratio of the volume of a pound 

 of steam at a given pressure to the volume of a pound 

 of water at the temperature of 39.1 degrees. This is 

 equal to the weight of a cubic foot of water at 39.1 

 degrees, or 62.425 Ibs., divided by the weight of a 

 cubic foot of steam of the required or given pressure, 

 as found in column 6. 



We have thus followed the results of the applica- 

 tion of heat to water and found that it is but the 

 taking of the energy of an already heated body, as 

 the fuel in the fire-box of the boiler, and transmitting 

 it to the molecules of the water, or, as better 

 expressed, it is transmitting the rapid vibrations of 

 the molecules of the fuel to the molecules of the 

 water until the latter are moving at such a rapid rate 

 and with such a swing that they overcome cohesion, 

 that mysterious attraction which particles of one 

 kind of matter have for each other, and tend to fly 

 apart, or as we say, expand, and this at a tremendous 

 rate. 



By taking advantage of this appreciable movement 

 of the molecules, we are able to do work or overcome 

 resistance with them. 



