FORMER GLACIATION OF NORTHEASTERN AMERICA. 379 



the water-shed on the south side of the Great Lakes is comparatively very 

 near them, so that the general direction of many of the .smaller streams is 

 southerly* Similarly, in Canada, the general course of the streams empty- 

 ing into the Lakes is southerly, with the exception of the Ottowa, which 

 nms nearly east. If it were not for the existence of the depression occupied 

 by the Great Lakes and a small ai^ea to the south of them, we might say 

 that throughout the region of the drift the general course of the streams is 

 to the south. But we have excellent reasons for believing that over a large 

 portion of the area at present occupied by the Great Lakes and drained to 

 the northeast, the water did, during a former and not very remote period, 

 flow towards the Gulf of Mexico. 



If, then, we had only to deal with those features of the Northern Drift 

 which have been already pointed out, namely, the existence, over extensive 

 regions, of detrital material, water-worn and more or less distinctly stratified, 

 having largelj' intermixed with it pebbles and boulders of rocks in place 

 somewhere to the northward, the difficulties to be overcome in solving 

 the problem of the oi-igin of this formation would not be insurmountable. 

 Borne out b}' a great number of focts, collected all over the world, some 

 of which have been laid before the reader in a previous chapter, we should 

 say that there was everywhere proof in the region in question, as Avell as in 

 so many others, that precipitation was once much greater than it now is ; that 

 the rivers and smaller streams having, over a large part of the Northern Drift 

 area, a general southerly direction, the detrital material abraded from the 

 rocks has been carried southward, just as we have seen that in the Sierra 

 Nevada, during a time of greater rain-fall, vast accumulations of gravel, 

 resembling in many respects those of the Northern Drift region, have been 

 spread out on the flanks of that range. 



In taking this view of the phenomena in question, we should — to a cer- 

 tain extent — be doing what was done by the earlier American geologists, 

 heads of the first great Geological Surveys of New York, Pennsylvania, and 

 other States, who were engaged in this work when the Northern Drift began 

 to occupy the attention of observers. They — Jackson, Hitchcock, Emmons, 

 James Hall, Mather, Vanuxem, Rogers, and others — all considered the 



* The insignificance of the area, on the south side of the Great Lakes, in which the drainage is towards them 

 is well Illustrated by the fact that the number of square miles of territory, in the United States, on the lake side 

 of the water-shed betn-een the Lakes and the Gulf of lIe.xico is only 175,000, while the area drained into the Gulf 

 of Mexico covers 1,725,000, or nearly ten times as much. 



