4°4 



ENGINEERING ON THE FARM 



as indicated by the arrows. A little very fine sawdust 

 placed in the water will show the action and direction of 

 the current, up on the upper side of the tube and down on 

 the lower side. This will circuit M to TV and will continue 

 until the water boils. It cannot be made any hotter than 

 this unless the top of the tube is closed. 



One thing to be noted is that the water at the bottom of 

 the tube has not become heated like that above the flame. 

 It has gathered some heat by being in contact with the water 

 above, but there was no circulation — the sawdust below the 

 flame did not move. The tube may be held by this lower 

 part all the time the upper part is boiling without burning 

 the fingers. This shows that there is nothing gained by 

 having a vessel extend below the source of heat. All water 

 below this point is excessive and has no value in a heating 



plant, for it does not 

 circulate. The proper 

 arrangement of heat and 

 water is shown in Figure 

 310. The water here is 

 all above the flame. If a 

 tube of this kind is ex- 

 tended through the floor 

 from the cellar and a flame 

 applied at the lower end, 

 we have, in principle, the 

 hot-water heating system. 

 The hot water will rise 

 from the base, give off 

 its heat to the air sur- 

 rounding the tube in the 

 upper room, and fall 

 again to the flame to be 

 reheated. The same tube might be extended to the 

 second floor and heat that also. If less heat is required, 

 the tube may be reduced in size and the water will not 



After University of Minnesota 



Fig. 309. Circulation of water produced 

 by the application of heat 



