IN CLOUDS AND RIVERS, ICE AND GLACIERS. 



109 



239. The maximum motion here is nine- 

 teen inches a day. Probably the eastern side 

 of the glacier is shallow, the retardation of 

 the betf making the motion of the eastern 

 slakes inconsiderable. The width of the 

 glacier here is 1)030 links, or about a mile 

 and a furlong. The theodolite was planted 

 high among ^the rocks on the western flank 

 ot' the mountain, about half a mile above the 

 Margelin See. 



35. MOTION OF MORTERATSCII GLACIER. 

 240 Far to the east of the Oberland, and 

 in that interesting part of Switzerland known 

 as the Ober Eugadin, stands a noble group of 

 mountains, less in height than those of the 

 Oberland, but still of commanding elevation. 

 The group derives its name from its most 

 dominant peak, the Piz Bernina. To reach 

 the place we travel by railway from Basel to 

 ZUrich, and from Zurich to Chur (French 

 Coire), whence we pass by diligence over 

 either the Albula pass or the Juliar pass to 

 the village of Pontresina. Here we are in 

 the immediate neighborhood of the Bernina 

 mountains. 



241. From Pontresina we may walk or 

 drive along a good coach road over the Ber- 

 nina pass into Italy. At about an hour above 

 the village you would look from the road 

 into the heart of the mountains, the line of 

 vision passing through a valley, in which is 

 couched a glacier of considerable size. 

 Along its back you would trace a medial 

 moraine, and you could hardly fail to notice 

 how the moraine, from a mere narrow streak 

 at first, widens gradually as it descends, un- 

 til finally it quite covers the lower end of the 

 glacier. Nor is this an effect of perspective ; 

 lor were you to stand upon the mountain 

 slopes which nourish the glacier, you would 

 see thence also the widening of the streak of 

 rubbish, though the perspective here would 

 tend to narrow the moraine as it retreats 

 downward. 



242. The ice-stream here referred to is tho 

 Morteratsch glacier, the end of which is a 

 short hour's walk from the village of Pon- 

 tresina. We have now to determine its rate 

 of motion and to account for the widening of 

 its medial moraine. 



243. In the summer of 18G4 Mr. Hirst and 

 myself set out three lines of stakes across the 

 glacier. The first line crossed the ice high 

 up ; the second a good distance lower down, 

 and t.he third lower still. Even thrj third 

 line, however, was at a considerable distance 

 above the actual snout of the glacier. Tho 

 daily motion of these three lines was as fol 

 lows : 



FIUST LINE. 



Stake 1 2 3 4 5 6 7 8 9 10 11 



Inches 8 12 13 13 14 13 12 ! 1J 7 5 



SECOND LINE. 



Stake. 1 2 3 4 5 6 7 8 9 10 11 



inches 1 4 6 8 10 11 11 11 11 H n 



TIIIRD LINE. 



Stake 1 2 3 4 5 G 7 8 9 n 11 



Inches 1 24 5 V 607755 4 



244. Compare these lines together. You 



notice the velocity of the first is greater than 

 that of the second, and the velocity of tho 

 second greater than that of the third. 



245. The lines were permitted to move 

 downward for 100 hours, at the end of 

 which lime the spaces passed over by the 

 points of swiftest motion of the three lines 

 were as follows : 



MAXIMUM MOTION IN 100 HOURS. 



First line 50 inches. 



Second line 4-4 " 



Third line 30 " 



246. Here then is a demonstration that the 

 upper portions of the Morteralsch glacier are 

 advancing on the lower ones. In 1871 tJie 

 motion of a point on tlie middle of the glacier 

 near its snout was found to be less than two 

 inches a, day ! 



247. What, then, is the consequence of 

 this swifter march of the upper glacier? 

 Obviously to squeeze this medial incline 

 longitudinally, and to cause it to spread out 

 laterally. We have here distinctly revealed 

 the cause of the widening of the medial mo- 

 raine. 



248. It has been a question much dis- 

 cussed, whether a glacier is competent to 

 sc'oop out or deepen the valley through which 

 it moves, and this very Morteratsch glacier 

 has been cited to prove that such is not the 

 case. Observers went to the snout of the^ 

 glacier, and finding it sensibly quiescent, 

 they concluded that no scooping occurred*. 

 But those who contended for the power 01 

 glaciers to excavate valleys never stated, or 

 meant to state, that it was the snout of the* 

 glacier which did the work. In the Morte- 

 ratsch glacier the work of excavation, which* 

 certainty goes on to a greater or less extent*, 

 must be far more effectual high up the val-, 

 ley than at the end of the glacier. 



36. BIRTH OP A CREVASSE : REFLEO 



TIONS. 



240. Preserving the notion that we are- 

 working together, we will now enter upon *k 

 new field of inquiry. We have wrapped up 

 our chain and are turning homeward after 

 a hard day's work upon the Glacier du 

 Geant, when under our feet, as if coming 

 from the body of the glacier, an explosion is 

 heard. Somewhat startled, we look inquir- 

 ingly over the ice. The sound is repeated,, 

 several shots being fired in quick succession. 

 They seem sometimes to our right, some- 

 times to our left, giving the impression that 

 the glacier is breaking all round us. Still 

 nothing is to be seen. 



250. We closely scan the ice, and after an. 

 hour's strict search we discover the cause of 

 the reports. They announce the birth of a 

 crevasse. Through a pool upon the glacier 

 we notice air-bubbles ascending, and find 

 the bottom of the pool crossedtoy a narrow 

 crack, from which the bubbles issue. Right 

 and left from this pool we trace the young 

 fissure through long distances. It is some- 

 times almost too feeble to be seen, and at no 

 Clace is it wide enough to admit a knite- 

 lade. 



