PEOPESSOE TYNDALL ON THE VEINED STEHCTHEE OF GLACIEES. 
295 
portions of the same seam, between 6 inches and 3 or 4 feet. I also found that a seam 
sometimes became forked so as to form two branches, which thinned gradually off until 
Tu!.15. 
they finally vanished. Fig- 16 is an ex- 
ample of this kind : the seam was divided 
at the point a ; one of its branches ran up 
the face of the crumple^ thinned off and dis- 
appeared at h ; the other widened con- 
siderably, but finally thinned off and also 
vanished. 
Along the bases of the crumples the fil- 
lets of water which poured down their faces 
weie collected and flowed. The streams thus formed ran in many cases alongside the 
existing veins of white ice, and had worn for themselves deep channels in the glacier. 
The thought soon suggested itself, that the seams themselves were formed by the gorging 
up of those channels by snow in winter, and the subsequent consolidation of this snow 
uming the descent of the glacier. Indeed the channels of the streams seemed the exact 
matrices of the seams of white ice*. 
The fact of one branch of a vein running up the face of a crumple, seems to prove that the ice, which 
at one time constitutes the lase of a crumple, does not always remain so ; the bases of the crumples are 
sometimes lifted up by the squeezing. The horizontal structure at the fronts of many of the crumples 
seems due to a local forcing forward of one protuberance over tliat next below it. Were the matter tested 
by strict measurement, I think it would be found that different portions of the crumples move downwards 
with different velocities. According to this view, upon the general motion of the glacier there are local 
motions superposed. 
2 E 2 
