16 THE WEATHER 



Methods of protection against frost (Wilson). 



Protection against frost is not only possible, but practicable. The 

 method to be employed depends on the kind of crop, the expense its 

 value will justify, and the facilities at hand. But whatever method 

 is chosen, it must be carried out systematically, intelligently, and with 

 thoroughness if satisfactory results are to be obtained. 



Progressive cranberry growers resort to three expedients to ward 

 off light frosts, aside from flooding, which is practiced in the spring and 

 autumn and also when exceptionally severe frosts are expected. These 

 methods are cultivation, drainage, and sanding. By cultivating the 

 marsh and keeping it free from weeds, moss, and other vegetation, the 

 heat from the sun more easily penetrates the soil, and there is, there- 

 fore, more heat to be given off when needed to prevent frost during 

 the night. Good drainage decreases the effect of cooling by evapora- 

 tion, and a dry soil becomes warmer under sunshine than a wet soil, 

 and therefore radiates heat more freely into the air at night when 

 needed to ward off frost. A covering of sand lowers the specific heat 

 of the soil, and thus stores up a large amount of heat during the day to 

 be given to the air at night. In the Cape Cod marshes it is the prac- 

 tice to spread about half an inch of sand over the surface of the marsh 

 each year. These methods, when systematically and carefully carried 

 out, are usually effective in warding off light frosts that are liable to 

 occur between early spring and autumn. 



Smudging has been practiced for many years in the trucking sections 

 of the Southwest, as well as in the fruit-growing districts of California 

 and Florida. The object is to cover the garden or orchard with a 

 thick blanket of smoke and vapor, with a view to checking radiation. 

 The success of this method depends upon the care and thoroughness 

 with which it is carried out. The cloud of vapor or smoke must cover 

 the garden or orchard, and be dense. A thin blanket will not be suffi- 

 cient. The fire should be built on the windward side of the orchard, 

 and such material used as damp straw, prunings, manure. 



If the fire burns briskly, it may be sprayed with water to increase 

 the cloud of vapor. 



Portable smudges have superseded the stationary smudge in many 

 places. They possess the advantage of being moved from place to 

 place, thus overcoming the effect of a change of wind, which often ren- 



