CLAYS. 161 



bricks. Its fossils arc Lecla Portlandica and Lucina flexuosa. The former was discovered 

 in 1836, in Portland, Maine, by the Principal of the Survey, who first called the attention 

 of geologists to these deposits. This species is probably extinct, while all the other shells 

 of the Champlain clays found in Vermont, are now found upon our coasts, and in the deep 

 water of Massachusetts Bay, &c. Prof. Adams says of them : " Since the industrious and 

 persevering efforts of several able naturalists in New England have resulted in the discov- 

 ery in the stomachs of fishes, of myriads of shells, of several species of Nucula without the 

 occurrence of a single recent Nucula Portlandica, we may safely infer that this species is 

 extinct. Lucina flexuosa, however, has been frequently found in such researches in a fresh 

 condition. Both the L. flexuosa and the congeners of N. Portlandica inhabit deep water 

 in fine dark blue silt, which needs only some pressure to resemble the Champlain blue 



clays." Both these shells are represented in Figs. 70 and 71. 

 " The blue clays, which contain no evidence of marine origin, 

 are insulated beds, scattered through the State, usually in val- 

 leys of various elevations. Very frequently they are overlaid 



Nucula Portlandica. , , ''., . ^ ,, , 



with deposits of muck or of marl, or of both, in the order ot 



71 - clay beneath, next above marl, and then muck. One case, however, is peculiar a 

 O large deposit in Cornwall and Shoreham, on the Lemonfair River, where blue clay is 

 overlaid with muck, which is succeeded by blue clay and then by another deposit of 

 muck. Probably the upper bed belongs to the newer pleistocene period, and the lower 

 bed being in the valley of the lake, may possibly have been of marine origin. 



"Some of these blue clays contain a considerable percentage of carbonate of lime, and 

 are admirably adapted for a heavy dressing of light soils. 



"Some beds contain a large proportion of sand, and in them we have often seen a grad- 

 ual transition from the blue clay beneath, to the fine sand above. No fossils have yet 

 been found in these insulated beds, but claystones, of the most beautiful forms and deli- 

 cate texture, are common in the finer varieties of blue clay." 



II. BROWN CLAY, SILT, SAND AND GKAVEL. 



The upper portion is not so constant in its lithological character as the loAver. As seen 

 by the heading, silt, sand and gravel are found associated with it, or take its place en- 

 tirely. But they are all characterized by the same fossils. T. S. Hunt analyzed the 

 brown clay, and found it composed of 



Silica, 49.70 



Alumina, ....... 31.20 



Peroxyd of Iron, with traces of Manganese, 6.60 

 Carbonate of Lime, ..... 3.47 



Carbonate of Magnesia, . . 2.30 



Water, ....". . 6.23 



100.00 



The specimen was from Middlebury. We think there is perhaps too great a difference 

 claimed between the two kinds of clay, the blue and the brown. We have seen speci- 

 mens of what we should have called brown clay in the place of the blue ; and would 



