42 SeijIm Lemsteöm. 



from 8,0 p. m. to 8,40 p. m. 7,8 degrees, or about 11° per hour 

 „ 8,40 „ „ 10,0 „ 6,8 „ „ 5,1 



whereas it remained very nearly constant from 



10,0 p. m. to 3,0 a. m. at — 2'',o 



On 15"' June the température was falling ail night, thougli in 3 hours 

 not more tlian 2°, 6 or about 0°,8 per liour. 



From this it will be seen, tliat the struggle between the three above- 

 mentioned causes on one skie and the radiation on the other side, results, 

 about on hour after sunset, in a position of equilibrium, which sinks but slowly, 

 proving that the l'adiation of heat prédominâtes. 



In this struggle, the purpose of the torches is to bring relief to the three 

 counteracting causes, in as much as they diminish the radiation by producing 

 smoke and moisture, and counteract the loss of beat: 



chiefly b}^ the same Condensed aq. vapour which falls down on the plants, 

 and also 



by the heat, which radiâtes directly from the torches, and by the motions 

 of the air caused by the strongei' heating in différent parts of the lield. 



From the account of experiments given above, it will be clearly seen that 

 the torches bave answered tlieir pni'pose well. 



In three cases out of foui-, the formation of hoai'-frost was prevented and 

 only a casual occurrence, i. e. a cold carrent of air, prevented this resuit from 

 being attained at the fii-st experiment. 



It must, however, be admitted that a formation of hoar-frost 7>iight hâve 

 occurred, if the température had fallen e. g. to — 0", but in any case, this 

 would bave occurred so shortly before suurise as to cause no damage. From 

 the preceding statement it is evident that even if ice and hoar-frost had been 

 formed, this would not hâve damaged the plants, provided that, during 1 i 

 hour before suiu'ise, the température had not fallen below - 2", near the grouud. 



On a doser examination of the results of the experiments, it will be found 

 that no damage would bave been done, even if the température in the field of 

 experiment had gone down to 3°, 2 (IV) and 3", 5 (III) below zéro near the 

 gi-ound, for the suri'ounding tîelds, were actually not damaged, though exposed 

 to such a low température ; indeed, fiom Experiment I \ve might infer that for 

 a short time the température may go down to — 4'',o near the ground without 

 causing any damage. 



