238 ANNUAL OF SCIENTIFIC DISCOVERY. 



of buried channels of excavation, and sometimes data enough 

 from which to map them out. Many other similar instances might 

 be adduced. 



"3d. Upon the glacial surface we find a series of unconsoli- 

 dated materials, generally stratified, called the drift deposits. 



" 4th. Above the Erie clays are sands of variable thickness 

 and less widely spread than the underlying clays. 



"5th. Upon the stratified clays, sand, and gravel are scattered 

 boulders and blocks of various sizes of metamorphic and eruptive 

 rocks, generally traceable to some locality north of the lakes. 



" 6th. Above all these drift deposits, and more recent than 

 airy of them, are the lake ridges, embankments of sand, gravel, 

 etc., which run imperfectly parallel to the present outlines of the 

 lake margins. 



" The history which I derive from the facts cited above is 

 briefly this : 



"1st. That in a period probably synchronous with the glacial 

 epoch of Europe, at least corresponding to it in the sequence 

 of events, the northern half of the continent of North America 

 had a climate comparable with that of Greenland ; so cold that 

 wherever there was a copious precipitation of moisture from 

 oceanic evaporation, that moisture was congealed, and formed 

 glaciers, which flowed by various routes towards the sea. 



" 2d. That the courses of these ancient glaciers corresponded 

 in a general way with the present channels of drainage. The 

 direction of the glacier furrows proves that one of the ice-rivers 

 flowed from Lake Huron, along a channel now filled with drift 

 and known to be at least 150 ft. deep, into Lake Erie, which 

 was then not a lake, but an excavated valley, into which the 

 streams of Northern Ohio flowed 100 feet or more below the 

 present lake level. Following the line of the major axis of Lake 

 Erie to near its eastern extremity, here turning north-cast, this 



f lacier passed through some channel on the Canadian side, now 

 lied up, into Lake Ontario, and thence found its way to the sea, 

 either by the St. Lawrence, or by the Mohawk and Hudson. 

 Another glacier occupied the bed of Lake Michigan, having an 

 outlet southward through a channel, now concealed by the heavy 

 beds of drift which occupy the surface about the south end of the 

 lake, -- passing near Bloomington, 111., and, by some route yet 

 unknown, reaching the trough of the Mississippi, which was 

 then much deeper than at present. 



"3d. At this period the continent must have been several hun- 

 dred feet higher than now, as is proved by the deeply excavated 

 channels of the Columbia, Golden Gate, Mississippi, Hudson, etc., 

 which never could have been cut by the streams now occupying 

 them unless flowing with greater rapidity and at a lower level 

 than they now do." 



With regard to the surface boulders, Dr. Newberiy says : 



" There is indeed no other conclusion deducible from the facts 



than that these sands, gravels, greenstone and other boulders 



have been floated to their resting-places, and that the floating 



agent has been ice in the form of icebergs; in short, that these 



