November 22, 1901.] 



SCIENCE. 



799 



and the ledges of limestone can almost be 

 traced continuously across it not far below 

 the lake surface, and as the elevation of 

 the bed rock surface around in Bay County 

 is, as Spencer and others have remarked, 

 considerably below the present lake sur- 

 face, it seems hard to assume that any 

 river used to flow northeast out of the Bay. 

 The results of my studies of the rock sur- 

 face topography of Huron County, published 

 in Volume 7 of our reports, based on the 

 extensive lists of borings catalogued there, 

 showed clearly a river system flowing 

 southeast, gathering strength. Again when 

 I came to discuss the general subject in 

 Water Supply Paper No. 30, it became 

 evident that the Saginaw lobe of ice did 

 not advance as far, proportionately, as 

 Michigan or the Huron-Erie, being re- 

 tarded, apparently, by this limestone ridge. 

 And, moreover, the result of borings for 

 coal, oil, gas and salt throughout the Sagi- 

 naw valley made it pretty clear that, be- 

 fore the ice age this valley did not drain as 

 at present, but to the west and northwest. 

 The evidence which I presented on this 

 point, in Water Supply Paper No. 30, was 

 very candidly accepted by Mr. Mudge, 

 who at the same time pointed out some 

 emendations in detail. Since, however, au- 

 thors are still following Spencer, it may not 

 be inappropriate to call attention to the 

 subject once more and to present some 

 of the elevations above tide which make 

 it reasonably certain that the drainage of 

 lower Michigan was to the northwest. 

 The coal basin of Michigan is surrounded 

 by a series of ramparts of which the sub- 

 Carboniferous limestone, Marshall sand- 

 stone, Devonian limestone and Niagara 

 limestone are the most important. It is 

 probable that in the neighborhood of Sagi- 

 naw Bay all these ramparts were broken 

 down by pre-glacial rivers, except the inner- 

 most, curved to the right and left, so that 

 finally when the ice overrode this the lobe 



extended in the general direction of the ice 

 motion, that of Saginaw Bay. The shore 

 of Saginaw Bay has now been so completely 

 lined with borings that it is not conceivable 

 that any valley of the first order 300 feet 

 below lake level can go out that way, 

 while it is only a few miles south, in Sagi- 

 naw County and west of it, that we find 

 bed rock elevations of only 300 and 400 

 feet below tide. The west part of the State 

 is so heavily covered with drift that our in- 

 formation regarding the bed rock surface is 

 much more scanty, but we know that in the 

 northwest part, bed rock surface is below 

 sea level. The great group of lakes re- 

 sembling somewhat the Finger Lakes of 

 New York, and the bays which are asso- 

 ciated. Great and Little Traverse Bays, re- 

 quire special explanation, and seem to find 

 it in some large pre-glacial valley that had 

 irregular pre-glacial topography, such as 

 would be found where the escarpments of 

 the middle and lower Devonian limestone 

 come close to master valleys. It seems to 

 me possible that before the last ice age the 

 main streams connecting the valley of Lake 

 Michigan with that of Lake Huron may 

 have passed from just north of Petoskey to 

 somewhere near Cheboygan ; at any rate, 

 there was aconsiderable stream there. So far 

 as the present indications of levels are con- 

 cerned, it would seem as though the streams 

 ivere flowing to the south rather than to the north, 

 but before we can settle this question, we 

 must hear from the geologists of other 

 States. 



The following papers were also read be- 

 fore the American Geological Society and 

 the Section. 



1. * Account of the Colorado Excursion ': 

 C. R. Van Hise. 



2. ' Junction of the Lake Superior Sand- 

 stone and the Keweenawan Traps in Wis- 

 consin ': U. S. Grant. 



3. ' Hydrographic History of South Da- 

 kota ': J. E. Todd. 



