4:4:8 H. 31. Brown — Clays of the Boston Basin. 



The till contained bowlders of varying sizes ; the largest over a 

 foot in diameter. Thickly intermixed as a part of a till was 

 a great deal of clay. The clay itself, belo^v the layers of sand, 

 was homogeneous and contained no foreign matter. The bot- 

 tom of the clay was seen in one instance only, and the clay 

 rested in that case on gravels. This exposure was at a distance 

 from the two mentioned above. 



Clays in Literature. — An early mention of the clays was by 

 Edward Hitchcock.- His conclusion stated that nearly all of 

 our clays are in the Tertiary formation. At the same time he 

 is frank in admitting that he has no evidence bearing on the 

 matter, and that his result was reached solely by analogy. The 

 European plastic clays resting on the chalk was the basis of his 

 reasoning. In the Geology of ]^ew Hampshire many cases are 

 instanced by Uphamf where clays overlie till. This is especi- 

 ally true of the Winnipiseogee Lake beds. His explanation is 

 quoted : " The ice-sheet probably remained in a high mountain- 

 like mass over these lakes after it had disappeared on each 

 side from the basin of Ossipee Lake and from the lower part 

 of the Pomigewasset valley. As the melting continued, the 

 drainage over this area was frequently obstructed because the 

 ice-sheet retreated from the lines of watershed towards the 

 middle of these hydrographic basins. The water seems then 

 to have melted large open spaces beneath the ice near its mar- 

 gin in which beds of clay and sand were deposited. This 

 would occu'r at the various heights and in the situation where 

 these beds are found, and the till which overlies them is shown 

 by its material to be that which was contained in the ice-sheet 

 and fell upon the surface when its melting was completed. 

 We thus see how these deposits came to be spread over the 

 slopes of the hills, thinly covered b}^ large boulders and till. 

 The frequent accumulation of such deposits in other parts of 

 the state was prevented by unobstructed drainage from the 

 melting ice. This modified drift over-laid by till does not 

 therefore appear to bear testimony to a warm interglacial 

 period, or even to any retreat and subsequent advance of the 

 ice." 



Emerson:}: reports clay resting upon till in the "JN'orthamp- 

 ton Lake " deposits. In a few localities he observes till over 

 clay, and, furthermore, explains the contortions of the clay beds 

 by ice moving over them. In the succession of events a minor 

 advance (being the third) of the ice is considered to explain 

 these phenomena. Shaler§ publishes a section' at Weewocket, 



* Eeport on Geology, Mineralogy, Botany and Zoology of Massachusetts. 

 1883, 36. 

 + G-eology of New Hampshire, iii, 136. 

 t Monograph 29 U. S. G. S., p. 697. g Bulletin 53 U. S. G. S., p. 16. 



