INTEKGLACIAL SANDS. 555 



its retreat from tlie seaboiird to a point north of Amherst, while the abun- 

 dant information concerning tlie character of the glacial deposits in Maine 

 and New Hampshire, pul)lished l)y Prof C H. Hitchcock, incline me to 

 the opinion that the recession continued at least to the foot of the White 

 Mountains. 



The middle layer of the till (3) in the cellar section is a compact, stony 

 clay, showing no distinction in color, compactness, or texture fronj either the 

 upper or the lower layer when exposed in fresh section. When frozen it 

 showed itself a little more sandy toward the north end of the section, evi- 

 dently because it had borrowed part of its material from the sands upon 

 which it rests. Its sharp horizontal line of demarcation from the sands 

 below I have already described. Its upper surface is, on the contrary, 

 most irregular. It sends many long, tortuous projections into the sands 

 above, which are bent over and spun out southward as the smoke of a 

 chimney is by strong wind, and indicate clearly the direction of the motion 

 of the ice. This structure is more manifest in the section itself than it 

 can be made in the drawing, and recalls the "fluidal" structure of many 

 volcanic rocks. Oftentimes filaments of the drift lie wholl}^ inclosed in the 

 sand, strung along in the direction and in the prolongation of one of the 

 })rojections, from which they have manifestly been separated. 



The upper layer of sand (4) is about 1 foot thick, and is somewhat 

 finer than the average of the lower stratum — about one-fourth inch — but 

 agrees with it under the microscope in degree of rounding of the grains. 

 It shows nowhere distinct traces of its former texture, this lia\"ing apparently 

 been wliolly rejilaced by a fine horizontal lamination, which seems to me 

 ratlier a pressure cleavage superinduced by the weight of the ice ujxin the 

 mass when frozen, while below it is confusedly interwoven with the till on 

 which it rests. Above it joins the third layer of till along a line nearly 

 horizontal, although the sand and the till are thoroughly molded tog-ether. 

 This is a second horizontal fault. Toward the north end of the section it 

 ends abruptly, being cut ofi" at right angles to its length, and the layers 

 of till above and below it come together, sejiarated only by a thin seam of 

 sand, which in places disappears entirely. 



Distinct traces of a second stratum of sand were to be seen in some of 

 the other sections I have described, and while the sand and second till 

 were often so confusedly interwoven that all indications of a second sand 



