OBSERVED IN SNOW CRYSTALS. 9 



sideration is_, that above Davos a layer of this southerly 

 wind intruded into the colder northerly winds ; and the ob- 

 servations of other days do not militate against this theory; 

 but as I have been able to compare but few days, I should 

 be glad to see a series of observations undertaken to obtain 

 further information. 



In Switzerland, the wind-observations are taken by the 

 anemometer placed near the meteorological station. Now 

 many of these are in the valleys ; and as the valley-winds 

 are so frequently merely local, these observations have little 

 value for our pui'pose, and the same for general me- 

 teorological purposes. On January 9th, when some of 

 the crystals were observed, the wind registered in the 

 valley at the meteorological station was north, while the 

 clouds (which I always noticed for my observations) showed 

 that a south wind was blowing above. 



I have called attention to the fact that I did not find the 

 classification of Scoresby^ always corresj)ond with what 

 I observed, finding sometimes low-temperature forms on 

 the coldest days. This may probably be explained by the 

 fact that in the Arctic regions there are fewer counter- 

 currents, and so the crystals were formed under more uni- 

 form circumstances : yet at the same time the only expla- 

 nation of the variety exhibited in each ci'ystal must arise 

 from growth taking place under slightly altered circum- 

 stances; else why should it suddenly change from one 

 type to another ? 



The amount of wind seems to exert quite as much influ- 

 ence upon the form of the crystal as does the temperature. 

 When there is little motion of the air the crvsta] can go on 

 building itself up regularly in all six directions ; but with 

 a considerable amount of wind the conditions for this 



* Voyage to Grreenland, 1823. 



