Boston Jleeting of the Geological Society. 217 
problems are to determine whether the till was mainly of subglacial 
origin; how much of the drift was of lacustrine and glacio-natant ori- 
gin; and to what extent the Pleistocene deposits of northern Missouri 
may be ascribed to flooded rivers. 
49. Remarks upon a supposed glaciated stone axe from Indiana. 
G. Frederick Wright, Oberlin, Ohio. The glaciated stone axe de- 
scribed by Mr. John T. Campbell in Science, vol. xxi, p. 346, for June 
23, 1893, was exhibited to the Society and commented upon by Profs. 
Wright, Niles, Hyatt and others. The general conclusion was that it 
was' a glaciated stone of such shape as to be readily utilized by the 
artificer, and that it had not been glaciated since the manufacture. 
.'>(). Pseudo-cols. T. C. Chamberlin, Chicago, 111. The theme of 
this paper is closely connected with the next, in the discussion of prob- 
able changes, effected during the Glacial period, in the courses of drain- 
age of the upper Ohio, Allegheny, and Monongahela rivers . The French 
term col is gradually coming into use to signify low passes or saddles 
on the watershed between drainage systems. Its use is very convenient 
in the discussion of reversed or diverted drainage, particularly that 
caused by the intrusion of glacial or igneous obstacles. It not infre- 
quently happens that, when a glacier enters the lower part of a drainage 
basin, it ponds back the waters, and causes them to pass over such a 
col into a neighboring basin. Sometimes the valley becomes perma- 
nently filled with glacial wash and morainic debris to such an extent as 
to cause the diverted stream to retain its new course after the retreat 
of the ice. In such cases the stream, in subsequently deepening its 
valley, forms a trench across the col, which gradually takes on the form 
of an ordinary valley. In time the col is only represented by a con- 
striction of the new valley and by certain residual features of the old 
topographic configuration. The floor of the trench across the col obvi- 
ously assumes the slope of the new stream that caused it and has its 
highest part on the up-stream side of the former col. As the trench is 
cut deeper and deeper, the highest point in the rock floor is gradually 
carried up stream. It may, in this way, be transferred some distance 
from the original col and may thus become entirely disassociated from 
its peculiar topographic relations. 
If, after this has been done, another glacial invasion ensues and the 
valley becomes again filled with glacial wash to some considerable 
hight, the transferred summit of the rock floor is liable to lose its obvi- 
ous connection with the old col and may perhaps seem to be associated 
with new and misleading topographic surroundings. In such a case, if 
the valley debris is penetrated by wells at only a few points and the in- 
vestigator ascertains thereby only imperfectly the nature of the trench 
and the location of the rock summit in its buried floor, he is liable to 
mistake this obscured rock summit for a true col. It is, in fact, not a 
col at all in any proper sense. It never has been a watershed, and has 
never performed the functions or sustained the relations of a true col. 
As there is frequent occasion to refer to this phenomenon in the dis- 
cussion of certain regions of reversed drainage along the border of the 
ancient glacial formations, I propose for it thedistinctivename pseudo- 
ail. The nature of the phenomenon has been more or less distinctly 
recognized by many geologists. The purpose of this paper is merely to 
bring it forth into more definite recognition, and to supply it with a 
convenient name, which may be used in lieu of the cumbersome peri- 
phrastic phraseology now required. 
•"»/. Certain features of thepast drainage systems of tin- upper <>hi<> 
basin. T. C. Chamberlin and Frank Lkvrrktt, both of Chicago, 111. 
This paper begins with a discussion of the probable old drainage 
basins. It supports strongly Mr. Carll's views, advanced some years 
ago, that the two uppermost sections of the present Allegheny basin, 
namely, the portion above the Kinzua col and that between the Kinzua 
