1887.] 441 [Upham. 



quently broken up through the wearing away of the sand underneath by 

 drainage. This layer or stratum was still intact on the north and south 

 and partially so on the east, in which direction it had, however, at certain 

 points, suffered some displacement by wagoning. It extended in a nearly 

 horizontal plane into the terrace, in the sloping edge of which the notch, 

 opening into its west bank and truncated at its edge, is cut. . . . 

 The quartz-bearing layer averaged a few inches only in thickness, varying 

 a little as the included pieces happened to be of smaller or larger size. 

 The contents were commonly closely compacted, so much so that one 

 might sometimes extract hundreds of fragments, many of them very 

 small ones, of course, from an area of considerably less than a square 

 yard. 



" The quartz bed, so far as examined, rested upon a few inches of sandy 

 soil, which passed downward into a coarse waterworn gravel, immedi- 

 ately overlying till. Above the quartz chips, stratified gravel and sand 

 extended up to the surface of the terrace. The pebbles of the gravel lying 

 directly on the quartz- bearing stratum were small and well rounded, and 

 were noticeably less angular than those of the gravel below. The stratum 

 of quartz chips lay at a level some twelve or fifteen feet lower than the 

 plane of the terrace-top. 



" These observations show that the quartz chips were spread originally 

 upon an ancient surface that has been since covered deeply by the modi- 

 fied drift which forms the terrace. It will be remembered that the quartz 

 chips and implements discovered by Prof. Winchell in this vicinity are con- 

 tained in the upper stratum of the terrace-plain; but the notch quartzes 

 do not occur at the terrace-top, and cannot have been derived from it, 

 but are confined strictly to a single stratum of the lower gravels closely 

 overlying the till. Hence the two sets of objects cannot be synchronous, 

 though they may have been produced by the same race at different stages 

 of its existence. The notch quartzes must, of course, be older than those 

 described by Prof. Winchell, by at least the lapse of time required for the 

 deposition of the twelve or fifteen feet of modified drift forming the up- 

 per part of the terrace-plain, above the quartz-bearing stratum." 



This description by Miss Babbitt shows that these implements 

 and fragments of chipped quartz occurred in a well defined thin 

 layer in the modified drift forming the glacial flood-plain of the 

 Mississippi river, as shown in the section which I have drawn (see 

 the following figure). I have examined the terraces and plains of 

 this valley drift from St. Paul and Minneapolis to Brainerd, some 

 twenty-five miles north of Little Falls, and find them similar in ma- 

 terial and origin with the modified drift terraces in the valleys of the 

 Merrimac, Connecticut and other rivers in New England. These 

 water-courses extending southward from the region that was covered 

 by the ice-sheet became the avenues of drainage from it during its 

 retreat. A part of the drift which had been contained in the lower 



