and the Crystallization of Ice. 413 



without seeing again the phsenomenon just mentioned. We may 

 suppose either that these observations were still too rare to 

 present some one of those neglected and apparently trifling cir- 

 cumstances that are requisite for the phsenomenon in question, 

 or that this depended also on the spot where I made my first 

 observation having been at a considerable elevation, and conse- 

 quently not far from the atmospheric stratum where the snow 

 was first formed. But then, as to the explanation of the ob- 

 served metamorphosis of snow, I think it might have some con- 

 nexion with the equally obscure property of some chemical 

 precipitates, which, like carbonate of lime, according to M. Ehren- 

 berg, consist, when first consolidated, of regularly arranged solid 

 globules, and which are then changed, " all of a sudden and quite 

 wonderfidly," to aggregates of true crystals of microscopic size. 

 (Confer Ehrenberg in Abhandlungen der Berliner Akademie,lS4<0.) 



Sunbeams seeming to melt the under surface of the ice of a river. 



{Reise urn die Erde, u. s. w., Histor. Abth. vol. ii. p. 407. 

 Travels in Siberia, &c. vol. ii. p. 513.) 



May 15, the temperature of the air varying between —5° R. 

 at sunrise and + 5° R. at noon ; and the elevation being 950 

 Par. feet (1012 English) above the sea. — Wherever we rode 

 today along the river Arka, or across it from one side of the 

 valley to the other, the efi^ects of the rapid thaw were visible. 

 The stream was quite free in the middle ; and at the sides the 

 thickness of the ice, though it varied considerably, was every- 

 where much diminished. It was very smooth and transparent, 

 and I saw beneath it an astonishing quantity of flattened air- 

 bubbles close together, and almost collected into a continuous 

 stratum. Where the ice was thinnest they were a foot in dia- 

 meter ; and a loud whizzing was heard in such places under the 

 feet of the reindeer as they broke through the thin covering of 

 ice. But the bubbles were always smaller where the ice was 

 strong, evidently because the air was frozen in during the 

 winter, and now, as the thaw advanced, it was liberated and col- 

 lected at the surface of the water. This proves directly that the 

 icy covering here was melted, not from above downwards, but iu 

 the opposite direction. It might perhaps be (but it was highly 

 improbable) that the scarcely warmer water from the middle of 

 the stream which was now open, had got to the banks* and 

 attacked the ice from below, or which is much more likely, that 

 the sun's rays passed inoperative through part of the transparent 

 ice, but developed and gave out their heat near its under side 

 ami when they fell on the surface of the water. 



• Tills event seems the more improbable as tlie river was shallow and 

 moved rapidly in a .stony bed. 



