January 



1903.] 



SCIENCE. 



2a 



with important chauges in the outlines and 

 relations of the ice lobes; and (11) the late 

 Wisconsin stage of mainly continued retreat, 

 with ten substages of halt or slight readvance; 

 marked by a series of that number of marginal 

 moraines and changes of the glacial lakes that 

 finally occupied the Erie and Ontario basins. 

 The chief part of the region is covered by the 

 Late Wisconsin drift and its moraines, which 

 in eastern Ohio extend to the boundary of the 

 glacial drift. 



Chapter III., filling a sixth part of the 

 volume, treats of the drainage systems, noting 

 in much detail the evidences of great modifi- 

 cations of the preglacial water courses. It is 

 shown that before the ice age probably the 

 upper and middle parts of the present Alle- 

 gheny Eiver were separately tributary to the 

 stream then flowing along the present bed of 

 Lake Erie; that the lower Allegheny and the 

 Monongahela, with the upper Ohio Eiver in 

 Pennsylvania, flowed also north to the old 

 River Erie by the valley of the Grand River; 

 and that many other changes from the ancient 

 courses of drainage also took place during the 

 glacial period along the Ohio River, thence 

 down to Cincinnati, where the ice sheet at 

 its stage of farthest advance reached across 

 that valley into the edge of Kentucky. 



Descriptions of the various drift forma- 

 tions, and especially of the moraines, occupy 

 the greater part of this monograph, which is 

 the second of a series giving the results of 

 Mr. Leverett's extensive field work. The first 

 was published three years ago, entitled ' The 

 Illinois Glacial Lobe,' and he has another in 

 preparation, to treat similarly of the glacial 

 and lacustrine geology of Michigan. His 

 elaborate studies of the ice age in this region 

 of the great Laurentian lakes, abounding with 

 very instructive records of the oscillations 

 and wavering departure of the continental ice 

 sheet, and comprising at last a complex his- 

 tory of many small and large ice-dammed 

 lakes, should be of much value as a basis of 

 text-books for the schools and colleges of 

 these states. 



As soon as the recession of the ice sheet 

 caused it to be a barrier on the northeast- 

 wardly sloping Erie basin, the water im- 



pounded there spread out as a lake, with out- 

 let past Fort Wayne to the Wabash River. 

 Its earliest stage is named Lake Maumee; a 

 later stage, when a lower outlet was uncov- 

 ered by the glacial retreat, past Ubly, in. 

 Michigan, is called Lake Whittlesey; and the 

 still later and most extended stage of this 

 body of water, reaching then into the Huron, 

 basin and outflowing, as Lake Whittlesey had 

 done, to Lake Chicago in the southern part 

 of the basin of Lake Michigan, retains the 

 name Lake Warren, which was proposed by 

 Spencer. The shores of these glacial lakes^ 

 marked by beach ridges of gravel and sand, 

 have been traced from Port Wayne east 

 through Ohio, along the Erie shore of Penn- 

 sylvania, and to the Finger Lakes and beyond 

 in central New York, where Fairchild has 

 identified the routes of later eastern discharge 

 by which Lake Warren was finally drawn, 

 away to the Mohawk and Hudson, being suc- 

 ceeded by the glacial lakes Algonquin and 

 Iroquois in the Huron and Ontario basins. 

 While the ice sheet was melting away, the- 

 land on which it had lain was uplifted from 

 a depression, so that the shore lines of th& 

 glacial lakes now have, along great portions 

 of their extent, an ascent to the north and" 

 northeast, varying from a few inches per mile 

 to a foot or more, and in some districts, 

 notably east of Lake Ontario, even as much 

 as five feet per mile. At the end of the lowan 

 stage of glacial advance, the deposition of 

 loess in the Missouri and Mississippi valleys, 

 and of a closely analogous silt formation in 

 the Ohio valley, as described in this report, 

 gives evidence of a depression of these regions 

 probably several hundred feet below their 

 present height. Before the accumulation of 

 the moraines in the Wisconsin stages of gen- 

 eral glacial recession, the greater part of the 

 Mississippi and Ohio basins, and the southern 

 part of the basins of lakes Michigan and Erie, 

 had been reelevated to nearly the same alti- 

 tude that they have since maintained with 

 only slight changes. But after the moraines 

 were formed, and during the existence of the 

 great glacial lakes on the northern borders of 

 the United States, much of their areas yet 

 remained depressed, as is known by the in- 



