120 The Principles of Fruit-growing. 



fan. A windmill may sometimes be set in motion 

 by water-power or other means. 



Heating the air. It is sometimes possible to di- 

 rectly heat the air by means of large fires, although 

 such practice does not seem to have generally met 

 with encouraging results. In the combined smoke 

 and vapor smudges which have been commended by 

 Hammon (page 112), the heat of the fire may add 

 something to the efficiency of the protection. The 

 strong currents of air which are set up by heavy 

 fires seldom aid in the protection of the plantation. 

 Yet there are cases in which hot fires have saved 

 trees over considerable areas from heavy frosts and 

 even from freezes. One of the best experiences in 

 this direction is reported from Florida by Da vies.* 

 In the freeze of February, 1895, he was able to 

 raise the temperature in his grove from 18 degrees 

 to 33 degrees by means of fires. "On the north 

 and west sides of your grove have what are called 

 conflagrations, big fires, that will send billows of 

 heat rolling between and over your tree tops ; and 

 all through your groves, at short distances, have 

 small fires to help on the good result." Mr. Davies 

 recommends that orange growers "get ready, and keep 

 ready all the time, for the freeze. Once it has come, 

 there will be no time for gathering materials for fire. 

 Your fuel must be on hand, and plenty of it." It 

 is then necessary to keep the fires burning vigor- 

 ously until the cold spell has passed. H. R. Ste- 



*D. O. Davies, "Protecting. Orange Groves from Cold," Fla. State Hort. 

 Soc. 1896, 28. 



