252 The American Geologist. October, i898 
11. The Volume Relations of Original and Secondary Minerals 
in Rocks. By Prof. Charles R. Van Hise, Madison, Wis. This 
paper discusses the volume relations of secondary minerals as com- 
pared with original minerals, and considers this volume change in 
reference to the depth at which the alteration occurs. 
12. Note on a Method of Stream Capture. By Alfred C. 
Lane, Houghton, Mich. When the divide between two streams is 
porous, and the valley of the one is much deeper than the other, 
springs may arise on the side of this deeper valley, which drain the 
water from the higher valley and thus diminish the erosive capacity 
of the stream therein, until the higher valley has a stream only in 
times of rain, and is soon eaten into by lateral tributaries of the deeper 
stream. Various illustrations of this action were given; and it was 
noted that during the Glacial period the streams draining the ice- 
front were especially liable to capture, because they occupied channels 
heavily filled with porous gravel and sand. 
13. The Development of the Ohio River. By Prof. William 
G. Tight, Granville, Ohio. A brief review of the literature shows 
that the generally accepted view has been that the Ohio river is a 
very ancient stream; but recently the work of several geologists in 
New York and Pennsylvania indicates the Pleistocene origin of the 
Ohio above New Martinsville. In papers already published by the 
author the existence of a very ancient erosion basin extending in 
general from east to west through the central part of Ohio and In- 
diana is established by the restoration of many tributary drainage 
lines and by deep wells. Further evidence is presented in this paper 
to show that the Ohio in its present location has been established 
through the appropriation of sections of numerous northwardly and 
northwestwardly flowing streams by the cutting of the ancient cols 
and the broadening and deepening of the valleys. The explanation for 
these changes is found in the position and action of the ice-sheet in the 
various sections, thus determining also the age of this part of the 
Ohio valley to be Glacial or Postglacial. The lines of discharge 
of the glacial waters determined the present lines of southwardly 
flowing tributaries of the Ohio. The preglacial drainage lines of the 
Ohio basin were intimately related to many features in the develop- 
ment of the Alleghany plateau and the great Appalachian valley and 
to the erosion basins in which the great lakes are found. 
The theory is proposed that the development of the Ohio river 
almost entirely beyond the greatest extent of the ice-sheet, and the 
development of the Missouri almost entirely within the limits of the 
ice, were due to the different angles which these streams made with 
the advancing ice-front, and to their dififerent gradients. In the Ohio 
basin the water was forced over distant cols; but in the Missouri basin 
it was drained southeastward along the ice-front, thus wearing back 
the ice at the time of final recession before the establishment of the 
channel by erosion. 
