On Night-Ffosts. 



35 



reaches the height of the ears of rye. Perhaps, this fact is partly the cause 

 of the rye being less sensitive to frost tliaii shortcr plants, for instance, 

 potatoes. 



In placing the thermometers, this circumstance was taken into considéra- 

 tion, and some of them were hung up near the ground, others on a levcl with 

 the ears of rye. In either of the points a and c there was a tiierniometer 

 near the ground and another 1,2 m. higher up; at points b and (/, one of the 

 thermometers was on a level with the cara and the otlier somewhat higher up. 

 The point c was situated 18 m. from the tield and was not untrequently under 

 smoke, so it is omitted here. The points /' and (j were at a distance of 45 

 m. from the tield of experiment, and point h by the l)ain, at 240 m. from 

 the same tield. All the torches were lighted at l(),3o p. m. and it is after 

 that time their eff'ect is to be examined. 



TAB. II. 



(10.40 p.m.) 

 (11,30 p. m.) 



On this occasion, as on the following, care was taken, in placing the 

 thermometers, to give them a situation the most unfavourable for heating, i. e. 

 to place them as far as possible from the torches. 



On examining, in Curve IIo Pl. I, the variations of température on the 

 12"' June, we find a very rapid sinking uiitil 10 p. m., but afterwards it 

 falls much more slowly, and at 11 p. m. it stands lowest, — 2",.^. At midnight the 



