ON SNOW. 75 



Such being the fa6ts, is it not probable, that a change of the 

 ivind is the caufe of fnozv ? 



Now let us examine, whether fuch a caufe will produce 

 fuch an efFeft. 



The winds that blow from any of the points between the Warm winds 

 South and the V/eji, by coming from warm climates, and pafT- JJ^J^'J^j,^*'";;'^ 

 ing over, perhaps, a very large traft of water, where there vapours in fnow. 

 is a powerful evaporation going on, muft poflefs a very great 

 degree of humidity, and are mofl: commonly, of a temperature 

 between 45" and 60** of Fahrenheit. 



The winds which blow from any of the points between the Namely, north- 

 Eaji and the North-Weft, by coming moftly from fuch high eafterly meeting 

 1 *•* J 1 /r ■ r c y^ c • l fouth-wefterly 



latitudes, and palling over immenle fields or jce, where eva- winds. 



poration is undoubtedly greatly impeded, cannot be fuppofed 

 to contain much water in folution, but muft bring with them 

 very great degrees of cold. 



Now let us fuppofe that a north wind of any temperature 

 between ^2'^ and 0° (which it generally is, in fuperior ftrata 

 of the atmofphere) meets a fouth-weft wind, as before-men- 

 tioned, tiie confequence will be, that the intenfe cold which 

 accompanies the former will convert the water with which the 

 latter is impregnated into ice; and the infiantaneous applica- 

 tion of cold is probably the reafon why fnow is produced in 

 what we cd\\ flukes ; for before the vapour can concentrate it- 

 felf into large particles, or drops, it is arretted by the intenfe 

 pold. 



In this view, the formation of fnow appears to be a beau- Formation of 

 tiful chemical phenomenon; for the warmer air, having a f'^pw. 

 greater affinity for the colder air than it has for the water which 

 is held in folution, the water is difengaged, cryftallized by the 

 cold, and precipitated in the form of fnow. 



It is generally obferved, that it is unufually cold for half an 

 hour or an hour before the fall of fnow, and warmer after- 

 wards. Might not this be accounted for, by confidering that 

 the adverfe wind mull meet with confiderable refiftance, in 

 effeding either a union with, or a paffage through a firatum of 

 air furcharged with water, and confequently muft be in a great 

 degree refleded back again, not in the perpendicular, but as 

 radii from a center, in an oblique direftion, part of which mud 

 defcend to the earth. And it will undoubtedly be warmer, 



after 



