Upon a REMARKABLE COLD. 169 



'That the difpofition of the air of thus parting with hoar-frqft, and 

 the cold which accompanies that feparation^ has a conftant depen- 

 dence upon the general ferenity of the atmofpbere, and is always in- 

 terrupted upon the fky being overcajl with clouds orfogginefs^ efpe- 

 cially near to the place of obfervation. 



THE analyfis which has now been detailed, though imperfect 

 in many refpects, feems, however, to demand our aflent to 

 thefe general proportions, how anomalous foever they may ap- 

 pear. 



THE nature or effence of the thing we call HEAT is fo far re- 

 moved beyond the immediate reach of our fenfes, that we 

 need not wonder though new facts relating to it come into 

 view, and even though they cannot immediately be traced up 

 to any general laws hitherto eftablimed. If, upon mature re- 

 flection, the prefent phenomena cannot be accounted for in 

 this way, they ought, on that very account, to challenge our at- 

 tention the more, as opening to us the neceffity of enlarging 

 oxir flock of principles, and inviting us forward to fo defirable 

 a work. 



IN the^/? proportion above laid down, it is afTerted, that the 

 cold produced is in proportion to the quantity of hoar-frofl fe- 

 parated from the air in a given time. This, however, muft be 

 underftood with fome limitation, and may not perhaps hold 

 true, if we compare together the degrees of cold and quantities 

 of hoar-froft feparated in different ftates of the air. 



THE import of the proportion only is, " That, at any given 

 " time, the more hoar-froft the air imparts to bodies over 

 " which it paffes in a clear ftate, the greater is the cold then 

 " produced." For it is very conceivable, that, according to 

 the different ftates of the air, in different feafons, or in different 

 nights of the fame feafon, arifing from its being more or lefs 

 charged with vapour, or perhaps with electricity, or fome other 



Y latent 



