SCIENCE OF THRESHING. 113 



by 10 ; the result will be the valve area in square 

 inches. 



The safety valve should be placed in direct connec- 

 tion with the boiler so that there is no possible chance 

 of cutting off the communication between them. 



THE STEAM GAUGE. 



The steam gauge indicates the pounds pressure of 

 the steam in the boiler. The article is too well known 

 to need special mention. 



So far there have been described the device in 

 which the steam is generated and a few of the acces- 

 sories by which note is kept of the condition of the 

 steam and water in its interior. It must not be lost 

 sight of that the boiler and its fire-box are but a means 

 to transfer the latent heat, that is, the rapid vibrations 

 of the molecules of the burning fuel, to the mole- 

 cules of the water in the boiler, which tend to cause 

 the latter to fly apart and thereby impart motion to 

 an engine piston. Remembering this fact, and that 

 it means dollars in the pocket of the engine owner 

 to have as many of these foot-pounds of energy trans- 

 ferred without loss as is possible, it is well to heed the 

 following hints. 



