112 The Principles of Fruit-growing. 



cold air may settle. The best smudges are usually 

 made by burning some tar -like substance. In any 

 ease, a smouldering fire is much better than a 

 blaze. The fire should burn slowly, and attendants 

 should keep the smudge going all night. Wet 

 leaves, manure, saw-dust, brush, grass, crude oil, and 

 a variety of materials are in use for smudges. 

 Some grape -growers cut the trimmings into short 

 lengths and pile them in the vineyard, expecting 

 to use them if frost should threaten. If frost does 

 not occur, the piles are burned before tillage is be- 

 gun. Crude petroleum stored in barrel -like tanks 

 or receptacles is sometimes conducted through the 

 plantation in pipes, and kettles are filled (and 

 ignited) at intervals. Galloway* says that a mix- 

 ture of one part gas -tar and two parts saw -dust 

 makes an excellent material for a smudge. 



Hammon writes as follows upon the use of 

 smudges : " One method of diminishing radiation 

 which is of considerable value, especially in a level 

 country, is the obscuring of the sky by means of 

 the smoke of smudge fires. This method has been 

 used with success in the level wheat fields of the 

 Dakotas and Manitoba, and should be of about 

 equal value in the broad interior valleys of Cali- 

 fornia. It is not so successful in the narrow val- 

 leys of a hilly country, for while it retards the 

 radiation of heat in the valley, the smoke bank is 

 asually of low elevation, and radiation proceeds un- 



*Year Book, U. S. Dept. Agr., 1895, 155. 





