On the Composition of Avanturine-Glass. 313 



wafts towards it a certain quantity of dust and other foreign 

 matters ; for, although the dust is less abundant in these re- 

 gions than in the valleys beneath, tempests are not wanting 

 which elevate it from time to time. But the stratum of snow 

 which is at the surface this year is covered the next by an- 

 other, and the dust which had accumulated upon its surface, 

 thus passes into the interior of the mass. At a later period, 

 this snow is transformed into ice, and as the dust it contains 

 is very fine, it will percolate, and probably circulate with the 

 water, across the capillary fissures, so as to be uniformly spread 

 throughout the mass. A direct proof that it is decidedly in 

 this manner that these occurrences take place, is supplied by 

 the fact, that the blue bands, in which water circulates much 

 more frequently than in common ice, likewise contain a much 

 more considerable quantity of gravel. This in no degree pre- 

 vents a portion of the gravel from remaining on the surface 

 of the beds, and hence their outcroppings are always more or 

 less soiled. 



We might cite, in confirmation of these observations, the 

 fact, that the ice, however pure in appearance, never supplies 

 a water that is perfectly limpid ; it always, more or less, ex- 

 hibits the milky hue which characterizes the water of all 

 glaciers ; and when it is left at rest, it usually deposits a 

 residue which is somewhat flocculent. Chemical analyses 

 of the water of glaciers have hitherto thrown no light on these 

 points. 



{To be continued.) 



On the Composition of Aimnturine-Glass. By Professor 



F. WoHLER. 



Artificial Avanturine is a brown Glass with included 

 small, very brilliant, spangles, which give it a peculiar shining 

 appearance. It was formerly employed for various articles of art 

 and ornament, and was manufactured at Murano, near Venice. 

 When my friend and colleague Professor Hausmann (to whom 



