Shaler.] 
462 
[Jan. 15, 
feet above the level of the sea. If this accumulation be really of 
glacial origin, it apparently establishes the height of the ice front 
in the Shenandoah, but as yet I must regard the indication as 
somewhat questionable. In the Alleghany Mountains west of Cov- 
ington, Va., there are deposits which I am disposed to consider of 
a glacial nature. At this point the deposits lie about 2000 feet 
above the sea level. These are the southernmost points at which 
I have found any satisfactory indications of glacial work, in the 
region south of the Potomac, and until further investigated, both 
of these deposits must be regarded as of doubtful character. 
In Europe in the region south of the Alps, we find the facts sim- 
ilar in their character to those existing in North America. Dur- 
ing the last glacial period the ice sheet extended down on to the 
Italian plains, unquestionably attaining levels less than 1000 feet 
of altitude above the level of the sea and probably occupying po- 
sitions not more than 500 feet above that level. From my obser- 
vations on the field I am disposed to think that the general mantle 
of the ice covered the southern face of the Alps down to within a 
few hundred feet above the sea. From one hundred and fifty to 
two hundred miles south of the Alps in the mountains of Tuscany, 
we have an extensive surface rising 4000 or 5000 feet above the 
sea. A careful search over much of this field showed me no evi- 
dence of occupation by ice. At the present rate of rise in the 
perpetual snow line in Switzerland we should expect an ascent of 
that plane about 1500 feet in passing from the foot of the Alps to 
the Apennine mountains north of Florence. We have thus a case 
similar to that we find in the North Carolina mountains in which 
there are elevations just south of the continental glaciers of a suffi- 
cient height to have been covered by ice under normal circum- 
stances, but where the evidence of such coating is conspicuously 
wanting. 
I have endeavored to apply the same considerations to the gla- 
cial phenomena of the Rocky Mountains, but the facts are as yet 
so imperfectly in hand that I have not been able to determine the 
relative attitude of the sheet in a satisfactory manner. This, how- 
ever, may be said, the distinct glacial accumulations in Colorado 
probably do not extend below the level of 6000 feet. As this re- 
gion is about on the parallel of the mountains of western North 
Carolina, it may perhaps indicate that the snow line lay through- 
out the southern parts of the United States above the summits of 
