132 PHILOSOPHICAL TRANSACTIONS. [ANNO 1 78 1 . 



there were gathered 2 portions of snow, the one from the surface, and the other 

 7 inches below it. The water produced from the 2 kinds was preserved in very 

 clean phials, in order to be compared together by some chemical trials, which 

 perhaps might throw some light on the whole of this matter. 



One other fact was new to me ; namely, the power of ardent spirits of dis- 

 solving snow, and consequently of producing with it a freezing mixture. The 

 alcohol and snow separately were at 8 degrees below the freezing point, and when 

 mixed suddenly and intimately, the temperature became in the space of 20 

 seconds 28° below O. This is a cold only 12° short of that which Fahrenheit 

 first produced by using spirit of nitre for the experiment ; and it is not improba- 

 ble, had the present experiment been tried with more precaution and address, 

 that the result would have been still more remarkable. There was employed 

 only about a pint of alcohol, but the proportion of snow was not then attended 

 to, and the thaw coming soon afterwards prevented a repetition of the 

 experiment. 



Postscript. — The water mentioned as produced from the superficial snow has 

 been examined by several chemical trials, with a view of discovering if it dif- 

 fered in any respect from the water obtained from snow gathered at considerable 

 depths, and near the ground. Had the atmosphere, when the thermometers 

 pointed so low, been disposed to furnish any saline principle, the union of such 

 an ingredient with the snow would have tended to produce an excess of cold at 

 the surface, similar to what was then observed. Or if the snow at these low 

 temperatures had acquired any remarkable power of dephlogisticating the air in 

 contact with it, a cooling process at and near the confines of the snow and air 

 might thereby have been maintained. In either of these cases, some very sen- 

 sible indications of a saline, or of a phlogistic principle, might be expected on 

 the water given by the snow collected from the surface. But in opposition to 

 both these views it remains now to be mentioned, that nothing of this kind did 

 appear in the course of the experiments, which indeed were contrived chiefly to 

 detect such circumstances. If therefore the arguments produced in both papers 

 on this subject will not allow us to account for so remarkable a cooling process 

 by an evaporation at the surface of the snow, it would appear, that there remains 

 still something unknown with respect to the cause. A proper investigation of 

 this matter, in climates favourable to such experiments, may possibly unfold some 

 further properties of beat with which at present we may be wholly unacquainted.* 



* This interesting subject was further prosecuted by the author during the winter of 1783- I , by a 

 variety of other experiments, of which he transmitted an account to Dr. Black, of Edinburgh, who 

 communicated the paper to the Royal Society, which hail been very recently instituted there ; and 

 which paper was afterwards published in the first volume of their Transactions, in 17.NN. We there 

 find that, from a careful review of all the experiments stated in that and the two former accounts, 



