THE aTKUGTUEE UF THE (JLAV. 707 



sands grade upward into the lean j)ortion of the layer, wliicli represents 

 the uniform high water of" the glacial river during the summer and which 

 is a true "gletchermilch," and this in its turn grades upward into the fat 

 deposits produced by the clarifying of the waters during the succeeding 

 winter. This would conspire with the fact that the mass of the coarse 

 material of these deposits has been brought in from the sides and moved but 

 little downstream, to indicate a low pitch for the valley during the time of 

 the glacial stream. 



THE TIME OCCUPIED IN THE DEPOSITION OF THE CLAYS. 



The considerations of the preceding section afford data for a calcula- 

 tion of the time occupied by the deposition of the clays, which is presented 

 as interesting rather than specially valuable. If we take the cla3's exposed 

 in the south of the Camp Meeting cutting and in the river bank adjacent, a 

 thickness of Di feet is exposed down to the water level, which would give, 

 at an average of two-fifths of an inch per layer, 2,155 years. If we take 

 the boring at the Northampton bridge, 113 feet, we have 3,390 years. As 

 these two neighboring sections are measured, the one up and the other down, 

 from the river level, we may add these two numbers to obtain a maximum 

 time for the deposition of the clays — 5,545 years. The erosion of the Deei'- 

 field and Westfield basins and the wearing back of Turners Falls in the 

 red sandstone a distance of 3 miles, with a width of about 60 rods and a 

 depth of about 40 feet, and of South Hadley Falls in the same sandstone 

 for a mile, with somewhat greater width and depth, will each give a measure 

 of the time that has elapsed since. 



ACTION OF ICEBERGS OR FLOES UPON THE CLAYS. 



Contorted days. — At a railroad cutting just west of the South Street 

 bridge in Northampton, already noted (p. 541) as showing sandstone and 

 till planed down together into a drumliu, the clays rest normally on both, 

 and a short distance eastward there begins a peculiar distorting, crump- 

 ling, and comminuting of the latter. At its worst the clays are thoroughlj^ 

 chopped up into small pieces, which are mingled in entu'e confusion. 

 This was exposed for a distance of about 33 feet, with a thickness of 2 feet. 

 Eastward about 50 feet, across a space where the exposure was only 

 sufficient to show that the clays were continuous and much disturbed, the}' 



