1846.] MOTION OF ICE OF GLACIER OF TALEFRE. 191 



B. At points not before observed. 



I had long wished to ascertain the motion of the ice, which 

 issues from the very remarkable basin-shaped glacier of Talefre. 

 That an oval circus or amphitheatre, whose length may be 

 roughly stated at 4000 yards, its breadth at 2000, entirely filled 

 with snow and ice (excepting the rocky island of the Jardin), 

 should disgorge itself by an icy stream through a chasm less 

 than 700 yards wide in its broadest part, appears to me, as I 

 have elsewhere stated at large,* a plain demonstration of the 

 viscous theory of glaciers ; the outlet in this case acting pre- 

 cisely as a stream does to a lake of indefinite extent, as a mere 

 overflow, or trop-plem, a fact only consistent with the quasi- 

 fluid motion of the mass so discharged. 



The great distance of the Talefre from habitable spots renders 

 it inconvenient for prolonged experiments ; but having last sum- 

 mer twice spent the greater part of a day in its neighbourhood, I 

 have been enabled to determine with exactness its rate of motion. 



The part which I selected for experiment will be under- 

 stood from the little portion of a map contained in Plate VIII. 

 fig. 2, on the same scale as my large map of the Mer de Glace. 

 The station marked W, near the foot of the Aiguille du Moine, 

 is a considerable block of granite, a few yards to the left of the 

 usual pathway ascending to the Jardin ; and my point of obser- 

 vation was permanently marked (as usual) by a cross cut in the 

 top of the stone, and painted red with oil colour, and the 

 letter W by its side. It is not many minutes' walk short 

 of the spot where travellers bound for the Jardin usually 

 enter on the glacier of Talefre. Hence it will, I hope, be easily 

 recovered. It is about 8700 feet above the sea. From it my 

 mark on the Tacul (station B of my map) could be distinctly 

 seen with the telescope ; and a transverse line across the glacier 

 of Talefre, in which marks were placed on the 24th July 1846, 

 made an angle, with the direction of B, equal to 98 30'. The 



* London Philosophical Magazine, May 1845, page 415. Compare the map of 

 the Mer de Glace in Travels in the Alps of Savoy. The outlet of the glacier is 

 seen in Plate VIII. fig. 2, accompanying the present paper. 



