PREVENTION OF SUMMER FROST 187 



The protection is believed to arise in several ways : firstly, 

 by the check to radiation produced by covering the field 

 with smoke ; secondly, by the upward movement of air 

 established round the field ; thirdly, by the actual heat pro- 

 duced. 



Lemstrom claims that the above plan has met with con- 

 siderable success in Finland. King has made some trials 

 of it in Wisconsin with no great result; he points out, 

 however, that success will be greatest when the frost is 

 most unseasonable, when, in fact, the general body of the 

 air is quite above the freezing point. Possibly, too little 

 attention has been given to the kind of smoke produced ; 

 the smoke furnished by damp materials should be the most 

 effective in preventing loss of heat by radiation. 



In the United States Agricultural Year Book for 1895, 

 p. 143, an account is given by B. T. Galloway of various 

 methods for preventing injury from frost employed in 

 California, and other parts of the States. Valuable fruit and 

 garden crops are protected by light wooden frames, 6x3ft., 

 on which oiled muslin is stretched ; the protection is said 

 to be nearly equal to glass. Movable screens, made of laths 

 fastened together with wire, are also employed, both for 

 protection against frost, and for shading from the sun ; 

 when not in use they can be rolled up. Some orchards 

 are provided with kettles of coal tar, placed at suitable 

 intervals, these are lighted with petroleum, and produce an 

 abundant flame and smoke. In other places cheap petro- 

 leum is carried by a main through the orchard ; when frost 

 is feared the petroleum is allowed to discharge into kettles, 

 and is set on fire. 



The most effective and elegant method for the prevention 



