276 PEOrESSOE TYNDALL’S OBSEEVATIONS ON THE !MEE DE GLACE. 
The descent of the ice through this gorge from the basin of the Talefie, ^ adduced 
by Professor iWs as an iilustration “wHch wUl appear to the unparhal reader 
aL^t a demonstration” of the principle of viscosity. “ The ice rs compact he urges, 
c and almost without fissures. .... The open crevasses which commence a httle above 
AB are turned towards the basin*.” The line AB here referred to “ 
the jaws of the gorge, and apparently at a considerable distance ‘ 
enters it. The description certainly would not apply to the rce of the year 18oo 
LonTbefore reaching tL summit of the faU the most skilful iceman wo^d fad hrmself 
in difficulties. We proceeded as far as we dared amrd the prts an c asms mto 
which the glacier is tom, and which followed each other so speedily, that the ndges 
between the fissures were often reduced to mere plates and wedges, whrch were in manv 
instances bent and broken by the lateral pressure. At some places vortrcal or s 
seemed to have acted upon the mass, and turned huge pyramids so far round as to p 
the structural veins at right angles to their normal positron. Looking do™war 
towards the summit of the cascade, the ice was frightfully nven. The glacier descends 
the cascade itself in wedges, pyramids, and columns, which latter often faU ^ 
like thunder, and crush to pieces the ice crags below them. After this descnptio 
not think that the case is likely to be accepted as a demonstration of the vjcosity of . 
I now pass on to the inclinations of the Glacier du Geant. For some distance belo « 
the base of the so-called Smcs the irregularities of the glacier render an es ima^e 
of its general inclination somewhat difficult, but I should judge it to be about lo . 
From the end of this steeper portion, two slopes, one of 4° 37', and the othei o o , ling 
u “ fa Tacul, and from this point to the bottom of the ice valley at Trelaporte we 
Tave the followi;g series of inclinations :-2« 15'; 3" 15'; 6» and 9»; thence to the Grand 
Moulin the slope is 3» 30', and afterwards, down the glacier ^ 3"; 
to the Grande Cheminde below I’Angle, the inclmations are o 10 ; 5 , fa -0, and . 
The glacier then descends a slope of 9°, and afteiwards passes the Montanvert at an 
inclination of 4° 45'. Below the Montanvert it falls steeply for some ffistance,^ le 
inclination being 16°. Between the base of this slope and the brow which mar -s le 
““n of L Mer de Glace and the commencement of the Glacier des Bois. the 
slope is 5° 10'. The ice afterwards descends an incline of 22 20 m a state ot grea 
location. From the base of this incline the general inclination of the lower portion 
“^rLfeTrefereiVto the Glacier de Lechaud will complete this portion of our subject. 
The upper portion of the glacier, to the base of the steep snow slopes which mar Bren - 
ISainst the Grande Jorasse, has an inclination of 4° 29'. Opposite to the ice fa 
of the Talefie, the inclination, for a short distance, is 3° IJ', and afterwards down to the 
Tacul where the Lechaud and Geant join, the slope is 5 22 . 
I vviU now endeavour to show the theoretic significance of the obsenations abo 
recorded, referring in the first place to the great terminal slope of the GUciet des Bois, 
* “Eeply to Hopkins,” Philosophical Magazine, 1845, vol. xxvi. p. 415. 
