348 J. D. Dana—Glacial Phenomena 
West Rock ridge, of nearly 300 feet, or half the whole amount 
it experienced before it landed. ‘T'wo other large bowlders lie 
near it. It is possible that these, and others of the bowlders, 
border has been stated above to be somewhat moraine-like. 
But it is largely a consequence of the fact that these hill-slopes, 
100 to 400 feet in height above the plain fronting them, faced 
obliquely the advancing ice, the trend of the border being 
north and south, and the flow of the ice S. 12°-85° W. Con- 
-~To understand the conditions at the south end of the great 
valley it is necessary here to consider the question as to the 
slope of the ice in the direction of the Connecticut valley on 
which the southward movement was more or less dependent. 
Wells River (a little north of the latitude of the White 
Mountains), is distant from New Haven about 200 miles, and 
from the south shore of Long Island, the supposed southern 
limit of the glacier, 240 miles. The height of the ice-surface 
about the White Mountains above the sea-level, according to 
.the best observations, including those by Professor C. H. Hitch- 
cock, was at least 6,000 feet and probably 6,500 feet. Assum- 
ing the. height to have been 6,000 feet and this level to have 
extended west-by-north (the probable direction of contour lines 
on the glacier) over the Wells River region, the slope of the 
ice along the 240 miles would have been about 0-17’, equal to 
42 feet in 1,000; or 25 feet per mile. Witb the height 6,500 
the slope would have been 5 feet in 1,000. Hither angle of 
slope is very small. In the Alps the lowest mean-slopes are 
23° to 3°, or 44 to 54 feet per 100, a rate ten times greater than 
the above; but the thickness of the ice there is not over 500 
feet. In Greenland, where the conditions were much like those 
of glaciated North America, the slope observed by Jensen over 
the Frederickshaab glacier* was 0°49’, or about 75 feet per 
mile; and.that measured by Helland on the glacier in the vicin- 
ity of Jakobshavn, 0°26’, or about 45 feet per mile. 45 feet to 
the mile would make the height of the ice-surface at Wells 
River over 10,000 feet.+ 
From such facts it would appear to be a safe conclusion that 
* Meddelelser om Grénland 1879, and this Journal, III, xxiii, 363, 1882. 
+ Even smaller angles of slope are stated to be sufficient to cause motion in 
