56 Selim Lemström. 



on at mid-niglit, instead of half an lionr later, the damage done would most 

 probably hâve been great. 



This is another prorf of how vecy little assistance is required by Nature 

 from the agrioulturist to ensure his crop from the threatening rmn. 



VIII 



METHODS OF PREYENTING THE RAVAGES OF 

 NIGHT-FROST. 



It bas ah-eady been demonstrated that the effects of radiation of heat can 

 be counteracted in two ways, namely: 



l:o by artiticial clouds of moistnre and smoke, or 2:o by motions of the 

 air, causing varions layers of air to blend, or by applying thèse two methods 

 at the same time. 



The first method bas, as seen from the experiments, given satisfactory 

 i-esnlts, which, in general, bave been confirmed by later expei'ience. 



The second meihod bas not yet had the benefit of an experiment, but 

 seems to promise well [See Note XI]. 



THE FIRST METHOD. 



Placing the Torches. 



Above ail, the field which is to be sheltered mnst be carefnlly examined, 

 to discover if a cnrrent of cold air from some bog-land sitnated on a higher 

 level, in the neighbonrhood, is to be expected. This cnrrent mnst be ont 

 off by means of torches placed not more than 2 meters apart. 



If the field lies in the open, in uieadow or bog-lands, the torches mnst be 

 placed ail l'onnd the field 3 meters apart (5 steps), and along the börders of 

 ditches at a distance of 15 meters from each other (25 steps.). If the field is 

 333 m in length and 300 m in breadth 

 with 33 plots and conseqnently 33 ditches of 300 m. 

 1,100 torches will be required, 50 of which shonld be held in reserve, to be 

 placed where the current of cold air may be stronger. 



For 5 hectares, rather more than half the number of torches, — abont 

 600, — will be necessary, and 50 more in reserve to preclnde a cold current 

 of air. 



