BY P. OLSSON-SEFFER, PH. D. 113 



Avoiding frost by means of smoke is since olden times well 

 known to the peasantry in Sweden and Finland, and during the 

 winter on many a frosty night well-applied smoke-producing 

 fires have saved valuable crops. 



The formation of artificial clouds consisting of smoke and 

 vapour must however be effected by fuel possessing the following 

 qualities : — 



It must be handy and cheap ; 

 It must be easily transportable ; 

 It must be easily kindled ; 

 It must burn slowly ; 



It must produce much smoke, vapour and heat ; 

 It must not be so inflammable that danger of spreading the 

 fire arises. 



It is of course very difficult to combine all these qualities in 

 one combustible. Professor Lemstrom has constructed a kind 

 of frost-torch for which he claims the said properties. 



These frost-torches consist of tubes of well-dried mud, and 

 of kindling cylinders which can be inserted into the tubes. 

 The torches may be placed in the field which is to be protected 

 and remain there all the time frost may be expected or until 

 they are used, for the rain affects only their surface and they 

 dry very soon. Frost-torches of this kind can be manufactured 

 at a price of less than ^d. apiece. 



For a description of these frost-torches and their use we 

 can refer to a leaflet by the inventor " On the method of pro- 

 viding against summer night frosts by the use of torches." 



The writer has had experience of these frost-torches and 

 found them to answer the purpose of producing a thick smoke. 

 They do not however burn long, and it is necessary to 

 determine the exact time when they are to be kindled, so as to 

 be sure that they are still producing smoke at sunrise, when the 

 danger is greatest. 



The inventor claims also for his frost-torches the property 

 of producing heat to such an extent as to affect a movement in 

 the air strata, thus bringing warmer air down for the benefit of 

 the vegetation. This effect is however still an open question, 

 and Homen among others is of a different opinion. 



Whatever kind of smoke producing fuel is used, it is how- 

 ever necessary to be careful when placing the fires so as to get 

 the use of all the natural conditions that will benefit, and to 



