292 Tlie American Geologist. November, 1899 
covered l\y the talus deposit. Subsequently, further erosion 
of the floor of the ravine removed the implement(?)-bearing 
t-tratum from its central portions, but left it around the edges 
to outcrop in practically the condition in which Miss Babbitt 
found it. On this theory we can easily reconcile Miss Bab- 
bitt's descriptions with the result of Dr. Holmes' researches. 
Indeed, if her very definite statement be absolutely correct, as 
I believe it is, I can conceive of no other explanation of the 
occurrence of a distinct quartz-chip-bearing stratum on the 
side of a ravine which cannot expose any of the original undis- 
turbed strata. This would place the age of the so-called imple- . 
ments later than the Glacial period, but yet quite ancient as 
compared with the present. 
I now wish to express, in a general way, the impressions 
which were received in the examination of the evidence stud- 
ied in my recent visit to central Minnesota: As others have 
pointed out, all the quartz chips of artificial origin, which are 
found in this region, were manufactured during the time tliat 
the quartz veins were exposed, namely, while the Mississippi 
flowed at nearly or quite its present level. These quartz out- 
crops could be reached soon after the ice-sheet had disap- 
peared from the immediate vicinity, but before the formation 
of the gravel and sand plain had proceeded far most of them 
were covered not only by the stream, but also by its deposits. 
While the upper five feet of the Glacial flood-plain was under 
formation, not one of the quartz veins in this county was 
above the stream-bed. Hence, as practically all of the flakes 
and other quartz fragments discovered by Prof. Winchell, Dr. 
Holmes and myself come from the upiper few feet of the glacial 
sand-plain, or from q much later flood-plain deposit, they 
must be of post-Glacial age. In the early part of the present 
period, when the trenching of the sand-plain to the present 
river-level had been completed, the quartz veins were again 
uncovered and the aborigines resorted to them for material to 
be used in fabricating their implements. So far the theory is 
absolutely safe ; but I am now going on to somewhat unstable 
ground. After the imcovering of the quartz in place, but 
before the formation of the Modern flood-plain, the widely- 
distributed chips on the higher terrace or Glacial sand-plain 
readied their present position. As we should naturally expect. 
