112 The Principles of Fruit-growing. 
eold air may settle. The best smudges are usually 
made by burning some tar-like substance. In any 
case, 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 
usually of low elevation, and radiation proceeds un- 
*Year Book, U. S. Dept. Agr., 1895, 155. 
