Upham.] 934 [April 2, 
ticular slopes gathered behind the shelter of higher ledgy hills, or 
upon their opposite sides. Except in this location, these slopes are 
like the lenticular hills, which seem to contain no ledge, being simply 
heaps of the ground-moraine fifty to two hundred feet in height. 
This resemblance suggests that both hills and slopes alike increased 
slowly in extent and depth without much change in place, new mate- 
rial being lodged upon their surface from the ice-sheet which swept 
over them. . 
The obscure lamination or cleavage, which is one of the character- 
istic features of the lower till, was probably produced by this mode of 
its accumulation. In this deposit from the ice-sheet, it corresponds 
to the stratification of sediments from water, but it is less distinct; 
and the fine detritus in which it appears contains glaciated pebbles 
and boulders indiscriminately mixed through its whole mass. This 
structure was at first thought to be a true cleavage, produced by the 
pressure of the glacial sheet. If we take this explanation, it still 
proves like the hardness and compactness which also mark the lower 
till, that this deposit was not ploughed up by the enormous pressure 
of the ice passing over it. How could this force permit the ground 
moraine to be heaped in the steeply-projecting lenticular hills? In- 
stead of this we should expect it to be left only in flattened sheets or 
behind sheltering ledges. The probable answer seems to be that the, 
finely pulverized detritus and glaciated stones in the bottom of the 
ice-sheet had a tendency to lodge upon the surface of any deposit of 
the same material. When such banks of the lower till became prom- 
inent obstacles to the ice-current, its levelling force was less powerful 
than this tendency of adhesion, which continually gathered new ma- 
terial, building up these massive rounded hills. At the melting of 
the overlying ice-sheet, the surface of hills and valleys, ground 
moraine and ledges, were alike covered by the nearly continuous 
mantle of the upper till. 
Mr. Wright presented a photograph illustrating the forma- 
tion of loess in the Missouri Valley, taken by Prof. Todd. 
Dr. B. Joy Jeffries showed some circulars issued by the 
Leipzig Museum of Ethnology, for the purpose of obtaining 
data relating to color perception and color-nomenclature 
among savage races. Data thus far obtained seem to show 
that savages have greater powers of discriminating between 
