ORCHARD HEATING 17 



frost they used considerably more to the acre. Oil in California 

 costs only about one-half what it costs in Utah, the investment 

 and crop are worth much more than in the Utah orchard, and 

 the freeze that they experience is the one that occurs on a still 

 night with a clear sky and with the whole community heating 

 simultaneously. The usual freeze in Utah is associated with 

 north winds after a rain, the sky clearing as the wind wanes, 

 after which the temperature falls quite rapidly. They report 

 average rises in temperature of more than GO F. as a result of 

 heating. Telephones are installed and the oil is piped through- 

 out the .orchard and the whole method including their coopera- 

 tive work on forecasting with the weather bureau has been 

 worked out to a nicety. They do not heat, as in other states, to 

 protect the buds but rather to protect the matured fruit and 

 occasionally the whole tree from freezing. 



COAL OB OIL AS FUEL 



From a study of the work of other investigators on the sub- 

 ject cif orchard heating, it is difficult to determine the relative 

 amounts of coal and oil burned per hour that will give the same 

 rise in temperature because there is considerable variation in 

 their results. For the purpose of making a comparison of the 

 cost of heating with the two kinds of fuel we will use the fol- 

 lowing statement from the Weather Bureau : "It is considered 

 that one ton of coal will equal 100 gallons of oil in heating 

 value." (k). Fifty heaters burning 40 pounds of coal would 

 have to produce the same rise in temperature as 100 heaters 

 burning a gallon of oil each in the same time interval, which is 

 no doubt only approximately true. The coal then weighs 2^ 

 times as much t-o produce the same result. A pound of oil gives 

 out very approximately \y 2 times as much heat so that if the 

 above quoted statement is correct, 1% times as much heat has 

 to be developed by the coal, in order to produce the same rise 

 in temperature as with the oil. More accurate data are needed 

 to make this comparison what it should be, but in the following 

 calculation we will use the above quoted figures. 



(k). Weather Bureau No. 542, Feb. 11, 1915, p. 577. 



