W. Hopkins on Changes of Climate. 253 
as 16,000 feet in that region, we have 4054, 4457, and 2500 feet 
for the descents of these glaciers below the snow-line. The two 
are in very near accordance with the mean of the cases 
above given; the last more nearly accords with the smaller de- 
Sceuts of the glacier of the Aar, and is probably due to a similar 
The glaciers which proceed from more limited spaces for the 
accumulation of snow and ice descend below the snow-line to 
much shorter than those above given. 
2, Height of the Snow-line, and Descent of Glaciers below it in 
the hypothetical cases of § I. 
The degree of cold requisite to produce glaciers on a mountain 
might obviously be caused by the elevation of the mountain. I 
Shall, in the first place, suppose former glaciers in western Eu- 
Tope to have been due to this cause alone, and determine the gen- 
eral elevation of that region which would be necessary to pro- 
such effects, rejecting the supposition, as altogether improb- 
able, that each individual mountain which exhibits glacial phe- 
homena was locally elevated independently of any corresponding 
elevation of the surrounding region. I shall then proceed to the 
thetical cases of the previous section. 
4. The present mean annual temperature of the Alps may be 
taken at 55°-5 F. (§ 13, p. 77); or 23-5 above the freezing 
temperature. The height of the snow-line is about 9000 feet, 
and that of the line of 32° F. abo 
ten 
elevation, equal to about 9300 feet ; and assuming’ the height of 
the snow-line to exceed this, as at present, by 2000 feet, the 
height of that line would be 11,300 feet. It is probable that the 
“aclets would not in this case descend quite so far below this 
line as at present. Suppose them to descend 4300 feet below it ; 
the height of their lower extremities would then be about 7000 
feet above the level of the sea. Consequently the glaciers would 
1 into the level of the lake of Geneva, provided the eleva- 
tion of the region placed that lake 7000 feet above the sea, or 
about feet above its present level. 
Henee, if blocks on the Jura have been transported from the 
Alps by the agency of ice, the Alps must, according to our pres- 
“nt hypothesis, have been at least 6000 feet higher than at pres- 
ber, Supposing the surrounding region to some extent to have 
~*n elevated at the same time. 
OND Sxnres, Vol. XV, No. 44,—March, 1853. 33 
