S9ij The American Geologist. june, isos 
ter was removed by erosion, as suggested, the intervals between 
the mounds wouhl not be strewed with gravel stones so thinly dis- 
tributed as to leave fairly good grazing for stock, but must have 
been abundantly' covered with pebbles and cobbles. Again, it 
would seem irrational to suppose that any conceivable wind cur- 
rent could sculpture these mounds by erosion. There remains no 
other eroding agent but running water flowing in some general di- 
rection. Hence these mounds must have been elongated with their 
major axes parallel with the flow. Currents of water of suflScient 
force to sweep not only the finer matter but a mass of coarse gravel 
one to two feet deep from between the tumuli, 3'et leaving the 
mounds standing as the}' now appear, also seem quite inconceiva- 
ble. Manifestly the facts that exist must exclude this hj'pothesis 
as well as those before noticed. 
In offering the following explanation of the origin of these 
mounds, I would hesitate to say that there can be no other wa}' to 
account for the phenomena, but must admit that I can see no other 
which will explain all the facts. At the least, it is earnestly hoped 
to enlist sufficient interest, if possible, to lead to a satisfactory so- 
lution of this question. 
There appears to be sufficient evidence to warrant a belief, that 
during the Glacial period this region was ploughed over b}^ moving 
ice. It lies within the southern edge of the drift-bearing area, as 
mapped by Chamberlin. The general appearance, however, would 
not warrant one to affirm that this locality was covered b}^ an ice- 
sheet moving in the same general direction as that east of the 
Rocky mountains, but rather of a local character, similar to those 
now existing in Alaska, which start from the crests of the mountains 
and flow in all directions into the valle3'S and onto the plains be- 
low, carrying forward and distributing the glacial drift as worn 
boulders, cobbles, sand, and gravel. During and after the retire- 
ment of the glacier, the drift was greatly modified by floods of 
water, the result of the wasting ice and frequent rains. East of the 
tumuli plain, the land, much of which is now under farm cultivation, 
gradually rises toward the remote mountains. \Yeris are sunk in ' 
this land from which to obtain water for domestic purposes. At 
the surface the soil is from one to three or more feet deep and 
overlies a coarse cobble drift, which is composed of material alike 
in character with that of the mounds. The wells pass through 
from six to ten feet of this cobble drift to a substratum of finer 
