PREGLACIAL GRAVELS NEAR BARABOO, WIS. 657 
eighteen inches deep, and about eight inches in diameter. When 
found, this was nearly filled with soil, but on removing the soil 
and the vegetation which grew in it, there was found at the 
bottom of the hole a small amount (a pint or so) of gravel, iden- 
tical with that at the site of the well. 
The fact that the surface of the quartzite on which the gravel 
under discussion rests, is market by pot-holes, suggests that the 
latter were developed when the former were deposited. The 
pot-holes have been observed before, and have been ascribed to 
glacial streams descending from the surface of the ice. But the 
surface where the observed pot-holes and gravel occur is beyond 
the reach of the ice of the last glacial epoch, and in this region, 
the ice of earlier glacial epochs is not known to have reached 
farther west than that of the last. The drift limit, as well as the 
ice limit in this region, is of exceptionally clear definition, so 
that it seems certain that the pot-holes are not moulins. 
It cannot be supposed that the gravel and the pot-holes are 
the product of glacial waters operating beyond the edge of the 
ice, first, because the crest of a high ridge where the gravel and 
pot-holes are, is not the place where extra-glacial waters would 
run, and, second, because the gravel itself is radically unlike the 
glacial gravels of the surrounding country, both in its litholog- 
ical constitution and in its physical condition. If similar mate- 
rials enter into the constitution of the glacial drift at all, they do 
so in very subordinate measure. It is incredible that running 
water, working upon the glacial drift of the region, could bring 
out of it chert, silicified fossils, quartz, etc., without the slightest 
admixture of any of the many other ccnstituents which make up 
the larger part of the drift of the region. The lithological con- 
stitution of the gravel is such as to make it altogether certain 
that it is not glacial, or aqueo-glacial. 
The physical condition of the gravel is hardly less conclusive 
than its lithological constitution, against its glacial or aqueo- 
glacial origin. The pebbles are rounded and smoothed to a 
degree altogether beyond that which characterizes the compar- 
able materials of the stratified drift. When the position, the 
