156 EXPERIMENT'S and OBSERVATIONS 



periments made in the year 1780, except in one inftance r 

 which fhall be particularly taken notice of in the fequel. 

 Agreeably to this, it was found alfo, that the fnow-fcale was 

 all the while gaining weight, as marked in the foregoing re- 

 gifter. From the regifter alfo, it is manifeft, that this depofi- 

 tion of hoar-frofl took place whilft the air was ferene, and 

 whilfl there was an excefs of cold at the furface of the fnow. 



FROM twenty minutes after eleven till half an hour paft one 

 in the morning, there were very plain indications of all thefe 

 fubftances furrendering to the air, though indeed flowly, the 

 hoar-frofl which had been before imparted to them ; whilft the 

 fnow-fcale, as is marked in the regifter, was lofing weight. 

 From the regifter it alfo appears, that all this happened when 

 the heavens were overcaft, and when the fnow upon the ground 

 was of a higher temperature than the air. 



DURING inoft part of the winter, the atmofphere was ex- 

 tremely liable to change from a ferene to a foggy or clouded 

 ftate, and vice ver/a. Thefe alternations affecting the cooling 

 procefs at the furface of the fnow, in fo particular a manner, I 

 was frequently led to repeat the obfervations and ftatical expe- 

 riments which have juft now been defcribed, without meeting 

 with any difference in the circumftances worthy of being men- 

 tioned. The phenomena of the nights of December 28. and 

 30. occurred frequently afterwards in the fame order, but 

 particularly in the night of January 25. when the heavens were 

 overcaft three times, and turned twice clear in the fpace of fix 

 hours. 



REMARKS. 



FROM the foregoing regifters, obfervations, and experiments, 

 as alfo from thofe of the years 1780 and 1781, it feems evident, 

 that the fnow continued colder than the air four feet above it, 

 only fo long as it was attracting hoar-froft at its furface ; and 

 that whenever this attraction ceafed, and even when it was fol- 

 lowed 



