550 Professor Tyndall, [June 4, 



from glacier orifices collected at the bases of the crumples, and 



FIG. 2. 



formed streams which cut for themselves deep channels in the ice. 

 These streams seemed to form the exact matrices or moulds of the 

 veins of white ice, and the latter were finally traced to the gorging up 

 of the channels of glacial rivulets in winter by snow, and the sub- 

 sequent compression of the mass to resistant white ice during the 

 descent of the glacier. The same explanation applies to the system 

 of bands upon the Glacier du Geant ; and the speaker was enabled to 

 trace the little arms of white ice which once were the tributaries 

 of the streams, to see the vein of white ice dividing into branches, 

 and uniting again so as to enclose glacial islands ; he finally traced 

 them to the region of their formation, and by sketches of 

 existing streams, taken near the base of the Seracs, and of bands 

 of white ice taken lower down, a resemblance so striking was 

 exhibited as to leave no doubt of the connexion between both. On 

 the walls of some deep crevasses which intersected the white ice 

 seams at right angles he also found that the latter penetrated the 

 glacier only to a limited depth ; having the appearance of a kind of 

 glacial " trap" intruded from above. 



But how is the backward dip of the blue veins to be accounted 

 for ? The speaker believed in the following way. At the base of 

 the cascade the glacier is forcibly compressed by the thrust of the 

 mass behind it ; besides this, it changes its inclination suddenly and 

 considerably ; it is bent upwards : and the consequence of this 



I jjfflHf lTTnr 



bending is a' system of wrinkles, such as those represented in 

 Fig. 3. The interior of a bent umbrella handle, sometimes pre- 



