74 Professor Tyndall^ [March 4^ 



tory experiment made by Nature herself with especial reference to the 

 point in question. Tiie squeezing of the mass, its yielding to the force 

 brought to bear upon it, its wrinkling and scaling off, and the appear- 

 ance of the veins at the exact point where the pressure begins to 

 manifest itself, left no doubt upon t!ie speaker's mind that pressure and 

 structure stood to each other in the relation of cause and effect, and 

 that the stratification could have nothing to do with the phenomenon as 

 here exhibited. 



He afterwards crossed the Strahleck, descended the glaciers of the 

 Aar, crossed the Grimsel, and examined the glacier of the Rhone. 

 This glacier has also its grand ice-fall. In company with Professor 

 Kamsay he climbed in 1858 the precipices which flank the fall at the 

 Grimsel side. In company with Mr. Huxley, he had in 1856 ascended 

 the heights on the Furca side of the fall. What he has stated regard- 

 ing the Grindelwald ice-fall is true of that of the Rhone ; the base of 

 the cascade is the manufactory of the structure ; and, as all the ice has 

 to pass through the mill, the entire mass of the glacier from the base 

 of the fall downwards is beautifully laminated. 



He afterwards descended the valley of the Rhone to Viesch, as- 

 cended the Egoishorn, and remained for eight days in the vicinity of 

 the great Aletsch glacier — the noblest ice-stream of the Alps. A 

 highly intelligent explorer had adduced certain phenomena of the 

 Aletsch glacier as an evidence against the pressure theory of the veined 

 structure ; and the speaker did not think himself justified in quitting 

 the place until he had perfectly satisfied himself that the glacier not 

 only presented no phenomena at variance with the pressure theory, but 

 exhibited some which seemed fatal to the theory of stratification. 



He subsequently proceeded to Zermatt, and spent ten days on the 

 RifFelberg, exploring the entire system of glaciers between Monte Rosa 

 and the Mont Cervin. These glaciers exhibit, perhaps, in a more 

 striking manner than any others in the Alps, the yielding of glacier 

 ice when subjected to intense pressure. The great western glacier of 

 Monte Rosa, the Schwartze glacier, the Trifti glacier, the glaciers of 

 St. Theodule, are first spread out as wide and extensive n^ves over the 

 breasts of the mountains. They move down, and are finally forced 

 into the valley containing the trunk, or Gorner glacier. Here they are 

 squeezed to narrow stripes, which gradually dwindle in width until 

 they form driblets, not more than a few yards across. From the 

 Gorner-grat, or from the summit of the Riflfelhorn, these parallel strips 

 of glacier, each separated from its neighbour by a medeal moraine, 

 present a most striking and instructive appearance. 



The structure of these glaciers was carefully examined, and in all 

 cases as the observer travelled from regions where the pressure was 

 feeble to regions where it was intense, the ice changed from a state 

 almost, if not entirely, structureless, to a state in which the veining was 

 exhibited in great perfection. Each glacier where it met the opposing 

 mass in tlie trunk valley, and was pressed against the latter by the 

 tlirust beiiind it, exhibited a beautifully developed structure. 



In a former discourse he had adduced proofs that the Glacier du 



