Upon a REMARKABLE COLD. 163 



materials I had colleded, and laid a thermometer upon each, 

 near the leeward fide, as ufual. 



THE refult was, that all, except the fnow, kept nearly of the 

 fame temperature, full fix degrees below that of the air, at the 

 fame height, and immediately to windward, which then was 

 + 12. The fand feemed rather the coldeft, and the fnow ob- 

 viou-fly neareft to the heat of the air. 



IN the mean time, the feparation of hoar-froft from the air 

 was very manifeft. It was moft difcernible to the fight upon 

 the fand and charcoal duft, though the manner of attaching 

 itfelf to thefe fubflances was very different. On the fand, it 

 fhowed itfelf by making the furface all over fparkle with an in- 

 finity of minute bright points, whilft, on the charcoal duft, it 

 fettled without fuch contiguity, and formed into many broken 

 filaments, of a dull hue, which here and there lay cluftered as 

 if aiming at fome ftellated arrangement. 



THE prefent experiment was made about midnight, when 

 the heavens were very clear, and the wind at eaft and one point 

 fouth, and fo brifk as to trail horizontally the flame of the 

 candle till it fometimes went out. Now and then this gentle 

 current came fuddenly ftraight downwards for a few feconds, as 

 was apparent from the manner in which it affected the flame of 

 the candle. 



So long as I was employed abroad at this time, there was no 

 fluctuation in the ftate of the atmofphere, nor any alternation 

 in the cooling procefs. Laft night, however, the cafe was very 

 different, as has been already mentioned. The experiments 

 then made were chiefly with the fnow-fcale and fand board. 

 When the heavens were overcaft, both foon acquired the tem- 

 perature of the air, which then was very ftill. It was found, 

 too, by ftatical experiments, that the fand acquired an addition 

 to its weight, when it happened to be for fome length of time 

 colder than the air ; but when the cooling procefs was inter- 

 rupted, and the fand continued for fome time of the fame tem- 



X 2 perature 



