412 Prof. Ermau on the Structure, the Meltiny, 



(fig. 3 c), because on their liquefaction there remained only the 

 middle of each plate, like an icy needle, in the water, until, the 

 new congelation ensuing, a number of needles ran at each side 

 out of this rib at angles of 60 degrees. 



Some of the stars were feathered in the beginning, but only 

 at the outer half of their rays. I did not see any change take 

 place in them, nor did this hap- 

 pen with some other more com- 

 plicated forms. Thus I observed 

 among others a small and con- 

 tinuous hexagonal plate, with 

 simple rays issuing like dia- 

 gonals out of its angles ; but 

 then each adjoining pairof these 

 rays was still connected by a 

 couple of needles which met at 

 an angle of 60 degrees (fig. 4). 



But these complicated forms 

 were comparatively rare; and 

 those transformed under my 

 eyes were so predominant, and 

 presented a spectacle so full of motion, that at last I could 

 hardly help comparing them with living beings. In fact, it is 

 only in the case of such that we are accustomed to witness 

 changes so mysterious without inquiring after the forces that pro- 

 duce them. We got, however, a partial explanation of this phse- 

 nomenon by remarking that the outer parts of the snow-crystal, 

 which were the first to melt, borrowed their warmth of liquefac- 

 tion from the parts that remained solid, and thereby cooled these 

 below the point of congelation. The newly-formed water could 

 then freeze again by its collecting round this cold ice, and by its 

 offering at the same time a smaller surface* to the air whose 

 temperature had melted the crystal. This water then assumed 

 in freezing a more complicated form, because the remainder of 

 the old crystal exerted in it a greater variety of attraction than 

 that which occurs in a wholly liquid drop. Perhaps all compli- 

 cated forms of snow result from the simple one by melting and 

 fi'eezing again in this way, a process which they must then un- 

 dergo during their fall through the air ; and heie this hypothesis 

 seemed somewhat confirmed by the complicated crystals being 

 always of less diameter than the simple ones. 



Additional remark [April \^^Q). — I have sometimes watched 

 the snow-crystals which fell at Berlin when the temperature of 

 the air was a little higher than the freezing-point, but till now 



* Viz. the curved surface of a single, or of six connected drops. 



