28 



THE APPLE 



periods, they will give as good satisfaction as the larger heaters. 

 With most heaters there is less heat given off as the oil burns low 

 in the pot, and a reserve supply of heaters should be on hand to 

 take care of this deficiency. In addition the temperature is usually 

 lower just before sunrise than at any other period, and the burn- 

 ing surface of the oil should be greater at this time than earlier. 



ng the distributing tank 



The standpipe in the rear contains the storage oil ; the oil runs by gravity through the pipe 



at the left. Note the nozzle for filling the heaters resting on the front wheel. (After Iowa 



State College) 



Number of heaters per acre. Of the smaller heaters, it will be 

 necessary to use from 80 to 120 per acre ; probably 100 is a good 

 average number to use. Of the larger pots, 60 to 80 per acre 

 should be used. It should be remembered that the smaller fires 

 scattered over the orchards are much better than a few large fires. 

 In using the large heaters it is not wise to reduce the number too 

 low, even though the burning surface can be made much larger 

 than on the smaller heaters. Moreover, in using a large number 

 of the larger heaters, the amount of the flame per heater can be re- 

 duced, thus giving greater reservoir capacity and long-continued fire. 



