Frost-protection by Means of Smudges 263 



of gunpowder being used. The guns are made of heavy 

 sheet metal, and are fired from beneath. The vmeyardists 

 think that the results have been satisfactory. The sub- 

 ject needs investigation. 



The making of smvdges. 



Frosts occur on clear nights. This is because the earth's 

 heat radiates quickly into space. When clouds or fogs are 

 present, this radiation is checked. It is possible, in many 

 cases, to supply a blanket of smoke to check radiation; 

 a,nd if this cover also contains much vapor of water, its 

 efl&ciency will thereby be greatly increased. 



The use of smoke or smudges to protect plants from 

 frost is an old practice. It is necessary, to secure the great- 

 est protection, that the smudge be dense and uniform, and 

 especially that it be maintained until all danger of frost 

 is past. The best results are usually secured on level 

 lands, where the smoke will not drain away, and where 

 there are no higher lands from which the cold 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, sawdust, 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 vineyards, expecting to use them if frost should 

 threaten. If frost does not occur, the piles are burned 

 before tillage is begun. 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. A mixture of one part gas-tar and two 



