﻿M. A. Heim on Glaciers, 507 



breadth of the glacier, in which crossed structure was distinctly- 

 visible — for example, in the fine ice full of white bubbles a blue 

 band one inch broad, cut at an angle of 40° by another of nearly 

 equal breadth, and others similar, even a complete system of 

 bands which crossed one another, as distinct as one could wish. 

 Further down the " structure-mill " the new structure was so 

 predominantly complete, that traces of the old were not easy 

 to find. 



In many other glaciers crossed structure is probably still 

 more readily to be found; and every thing will be more regular 

 when the fall is not so wild and the structure is better developed 

 in the upper part than in the Rhone Glacier. 



The bounding surface between bubble-free (blue) ice-band 

 and bubbly (white) ice can be readily laid bare in a hand spe- 

 cimen by a carefully directed stroke. It immediately strikes 

 one that it is cylindrically grooved vertically. At the first glance 

 the following explanation obtrudes itself : — The paths which, in 

 the formation of the blue band, the retreating air-bubbles have 

 taken are preserved, filled with ice, reminding one of kernels in 

 stone; and in isolated cases the air-bubble does not urge its 

 way quite to the top, it stays at the end of the ice-kernel which 

 marks its unfinished path. How much this observation sup- 

 ports Professor TyndalPs explanation of the origin of the blue 

 bands in the white ice is obvious. I made it first on the Upper, 

 then on the Lower Rhone Glacier, and afterwards found it con- 

 firmed in other glaciers. Fig. 15 (Plate VII.) represents a piece 

 of white glacier-ice in which the bounding surface of one of 

 the blue bands is laid bare. 



When the minute displacement-fissures are no longer opera- 

 tive as such, the water in them at length freezes to a bubble- 

 free narrow ice-vein of at most 1 centim. thickness. This is 

 readily distinguished from the blue bands by its regular course ; 

 it has a somewhat different aspect; in addition to which it 

 usually cuts the structure at a slight angle, as is frequently to 

 be seen in the walls of the normal open fissures (in fig. 16, a is 

 the ice-vein). On the left side of the Rhone Glacier these 

 glacier- veins are found pretty numerous both immediately above 

 and below the fall. I have never seen on their bounding surface a 

 cylindrical structure. This is at once explained by their different 

 manner of formation. 



Far more suitable than any other glacier for the study of the 

 origin of the dirt-bands and structure is the Trift Glacier, which 

 on the Triftlimmi is connected as a neve cap with the Rhone 

 Glacier, but descends in the opposite direction, into the valleys 

 to the north. Its principal fall is incomparably more magnifi- 

 cent and wild than that of the latter. Thence in a length of 



