186 RELATIONS OF SOIL TO HEAT 



1 1 ,000 ft. above the sea, were in the habit of burning heaps 

 of manure as a sacrifice to the sun on clear nights, in order 

 to secure the protection of the maize from frost. Boussin- 

 gault mentions that the same practice of producing smoke 

 as a protection against frost is employed in some of the 

 vineyards and olive gardens in France ; the smoke is needed 

 only in the early morning from 3 a.m. to sunrise. 



Lemstrom in Finland has recently developed this plan 

 of protection, with the view of diminishing the serious losses 

 from which his countrymen suffer (Exp. Stat. Record, v. 660). 

 Later information as to the method is given by King (Wis- 

 consin 12th Report, 253). Hollow cylinders of peat mud 

 are moulded by machinery; their length is TO inches, their 

 external diameter 7 inches, their internal diameter about 

 T | inch. Each cylinder, or torch, is provided with a smaller 

 lighting cylinder, about 2 inches long. When the torch is to 

 be kindled, the smaller cylinder is wetted with petroleum, 

 and inserted a little more than its own length into the larger 

 cylinder, which is placed in a sloping position; a light is 

 then applied. The larger cylinders are kept in their places 

 in the field ready for action. If the field is in the midst 

 of level ground, it is surrounded by torches, one being 

 placed at every five steps ; torches are also placed across 

 the field at every twenty-five steps. If the field is exposed 

 in any direction to currents of cold air, these must be cut 

 off by placing torches at every three steps. If, on the other 

 hand, it is protected by a wood, or is intersected by ditches 

 which do not enter it from a higher level, then the number 

 of torches may be diminished. The number of torches 

 required for one acre is reckoned as 90-130 ; for five acres, 

 270-320 ; for ten acres, 500-550; for twenty-five acres, 1,100. 



