100 



THE FORMS OF WATER 



once. The crevasses change within certain 

 ]imits from year to year, and sometimes from 

 month to month ; and this could not be if 

 the ice did not move. Rocks and stones also 

 are observed, which have been plainly torn 

 from the mountain-sides. Blocks seen to 

 fall from particular points are afterward ob- 

 served lower down. On the moraines rocks 

 are found of u totally different mineralogical 

 character from those composing the moun- 

 tains right and left ; and in all such cases 

 strata of the same character are found bor- 

 dering the glacier higher up. Hence the 

 conclusion that the foreign boulders have 

 been floated d ,wn by the ice. Further, the 

 ends or " snouts" of many glaciers act like 

 ploughshares on the land in front of them, 

 overturning with slow but merciless energy 

 huts and chalets that stand in their way. 

 Facts like these have been long known to the 

 inhabitants of the High Alps, who were thus 

 made acquainted in a vague and general way 

 with the motion of the glaciers. 



ID. THE MOTION OF GLACIERS. MEASURE- 

 MENTS BY HUGI AND AQASSIZ. DRIFTING 

 OF HUTS ON THE ICE. 

 140. But the growth of knowledge is from 

 vagueness toward precision, and "exact de- 

 terminations of the rate of glacier motion 

 were soon desired. With reference to such 

 measurements, one glacier in the Bernese 

 Oberlaud will remain forever memorable. 

 From the little town of Meyringen in Swit- 

 zerland you proceed up the valley of Hasli, 

 past the celebrated waterfall of Handeck, 

 where the river Aar plunges into a chasm 

 more than 200 feet deep. You approach the 

 Grimsel Pass, but instead of crossing it you 

 turn to the right and follow the course of "the 

 Aar upward. Like the Rhone and the 

 Arveiron, you find the Aar issuing from a 

 glacier. 



147. Get upon the ice, or rather upon the 

 deep moraine shingle which covers the ice, 

 and walk upward. It is hard walking, but 

 af'.er some time you get clear of the rubbish, 

 and on to a wide glacier with a great medial 

 moraine running along its back. This mo- 

 raine is formed by the junction of two branch 

 glaciers, the Lauteraar and the Finsteraar, 

 which unite at a promontory called the Ab- 

 Rchwung to form the trunk glacier of the 

 Unteraar. 



148. On this great medial moraine in 1827 

 an intrepid and enthusiastic Swiss professor, 

 Ilugi, or Solothurm (French Soleure), built 

 a hut with a view to observations upon the 

 glacier. His hut moved, and he measured 

 its motion. In the three years from 1827 

 l:> 1830 it had moved 330 feet downward. 

 In 1833 it had moved 2354 feet ; and in 1841 

 M. Agassiz found it 4712 feet below its first 

 position. 



140. In 1840, M. Agassiz himself and some 

 bold companions took shelter under a great 

 overhanging slab of rock on the same mo- 

 raine, to which they added side-walls and 

 other means of protection. And because he 

 wad his comrades came from Neufchatel, the 



hut was called long afterward the " Hotel 

 des Neuch&telois." Two years subsequent 

 to its erection M. Agassiz found that tke 

 " hotel " had moved 486 feet downward. 



20. PRECISE MEASUREMENTS OF AGASSIZ 

 AND FORBES. MOTION OF A GLACIER 

 PROVED TO RESEMBLE THE MOTION OF A 

 RIVER. 



150. We now approach an epoch in the 

 scientific history of glaciers. Had the first 

 observers been practically acquainted with 

 the instruments of precision used in survey- 

 ing, accurate measurements of the motion of 

 glaciers would probably have been earlier 

 executed. We are now on the point of see- 

 ing such instruments introduced almost si- 

 multaneously by M. Agassiz on the glacier 

 of the Unteraar, and by Professor Forbes on 

 the Mer de Glace. Attempts had been made 

 by M. Escher de la Linth to determine the 

 motion of a series of wooden stakes driven 

 into the Ak-tsch glacier, but the melting 

 was so rapid that the stakes soon fell. To 

 remedy this, M. Agassiz in 1841 undertook 

 the great labor of currying boring tools to 

 his " hotel," &nd piercing the Unteraar 

 glacier at six different places to a depth of 

 ten feet, in a straight line across the glacier. 

 Into the holes six piles were so firmly driven 

 that they remained in the glacier for a year, 

 ami in 1842 the displacements of all six were 

 determined. They were found to be 160 

 feet, 225 feet, 209" feet, 245 feet, 210 feet, 

 and 125 feet, respectively. 



151. A great step is here gained You 

 notice that the middle numbers ar^ the larg- 

 est. Tiiey correspond to the central portion 

 of the glacier. Hence, these measurements 

 conclusively establish, not only the fact of 

 glacier motion, but that tJie centre of the 

 glacier, like that of a river,- moves more rapiily 

 than the xidea. 



152. With the aid of trained engineers M. 

 Agassiz followed up these measurements in 

 subsequent years. His researches are record- 

 ed iu a work entitled " Systeme glaciaire," 

 which is accompanied by a very noble atlas 

 of the Glacier of the Unteraar, published in 

 1847." 



153. These determinations were made by 

 means of a theodolite, of which I will give 

 you some notion feanediately. The same 

 instrument was employed the same year by 

 the late Principal Forbes upon the Mer de 

 Glace. He established independently the 

 greater central motion. He showed, more- 

 over, that it is not necessary to wait a year, 

 or even a week to determine the motion of a 

 glacier ; with a correctly-adjusted theodolite 

 he was able to determine the motion of vari- 

 ous points of the Mer de Glace from day to 

 day. He affirmed, and with truth, that the 

 motion of the glacier might be determined 

 from hour to hour. We shall prove this 

 farther on (162). Professor Forbes also tri- 

 angulated the Mer de Glace, and laid down 

 an excellent map of it. His first observa- 

 tions and his survey are recorded in a cele- 

 brated book published in 1843, and entitled 



