242 DYNAMICAL GEOLOGY. 



Island (7000' high) in lat. 53° 10' S., long. 73° 30' E., several glaciers were seen which 

 came down to the coast-line, and made cliffs of ice on the shores. On the New Zealand 

 Alps, whose peaks are 7500' to 12,350' in height, there are glaciers, of which the Tasiuan 

 is 18 miles long and 2 wide. The snow-line is at 5000', and the ice descends on the 

 west side to 600' above the sea. 



The so-called hanging -glaciers occur about steep slopes of many glacier regions, as 

 the peaks of the Mont Blanc region, and between the snow-covered plateau of Norway 

 and the sea. Reconstructed glaciers (glaciers remaings) are made out of the fallen ice of 

 avalanches by regelation. At the Jokuls Fiord is a fine example of it. Geikie, describ- 

 ing it, says the ice slips off in occasional avalanches from the edge of the high snow-field 

 into the defile, and there becomes recemented into a tolerably solid mass, which moves on 

 as a glacier, and continues to the sea level. 



2. The Flow of Glaciers. 



1. Conditions of Jloio. — In addition to the relations of glaciers to rivers 

 already mentioned, there are the following : — 



As with rivers : (a) Friction impedes flow along the sides and bottom, 

 and consequently the most rapid movement of the glacier is along the mid- 

 dle portion above. This effect is least in large and deep streams, and at a 

 minimum in great continental glaciers. 



The more rapid flow of the middle at the surface of the stream is proved 

 by the observation that a straight transverse line marked by poles set up in 

 the ice (ab) becomes a curved line (cd) in consequence of 

 the movement ; also by the fact that the transverse cre- 

 vasses of glaciers become arched in front, as in the Rhone 

 Glacier (Fig. 207), and that transverse dirt bands become 

 similarly arched (right half of Figs. 205, 206, Forbes, Tyndall), repre- 

 senting the condition in a tributary glacier, the G6ant, after union with 

 other tributaries on the left (page 235). Further, the retardation at bot- 

 tom is proved by the fact that vertical blocks made by transverse crevasses 

 take an up-stream dip, which gradually increases with the flow. (Guyot, 

 1838.) 



(&) At a bend in the stream, the movement is more rapid on the convex 

 side than on the concave ; and the medial line of greatest rapidity is nearest 

 the convex side. 



(c) When the stream abruptly narrows, the ice above becomes more or 

 less heaped and slower in movement, and then passes the narrows with an 

 increased rate of flow. 



(d) On passing small rocky islets, the glacier sometimes bends about 

 the obstacle and envelops it without breaking, as in the case of two islets 

 of rock in the midst of the Brenva Glacier, showing a molecular adjustment 

 in the ice. (Guyot, 1838.) 



But, unlike rivers: (e) Winds neither impede nor accelerate the sur- 

 face movement; and (/), as with other solid substances, the yielding to 

 resistance is commonly attended by fractures called crevasses, and by dis- 

 placements. 



d 



