CLAYS. 167 



" The deposits of this blue clay at the foot of the Great Falls in Milton, at the foot of the bank on the lake 

 shore a little north of Clay Point in Colchester, and along the new road below Winooski Falls in Burlington, 

 are among the finest I have examined. 



" A large proportion of our pleistocene formation consists of a mixture of sand and clay, lying usually 

 above the finer blue clay, and below the fine silicious sand. The fossils, though found in the sand and 

 occasionally in the blue clay, are most abundant and best preserved in this mixture of sand and clay. 

 Probably nine-tenths of the shells in these formations belong to one marine species, the Sanguinolaria 

 fusca, or T. Greenlandica of Prof. Emmons' New York Geological Report. The next most common species 

 is the Saxicava rugosa. The localities of marine shells are too numerous to be particularized. I will, 

 however, mention some of the most important, beginning at the south. On the road running east about 

 half way from McNeil's landing in Charlotte, to Charlotte village, marine shells, though in not a very good 

 state of preservation, may be seen in the ditches excavated by the side of the road. About a mile northeast 

 from McNeil's landing, at a place called Holmes' Bay, fossil marine shells are very abundant, and are well 

 preserved. They are embedded in the sandy clay bank, most abundant about 10 feet above the water of the 

 bay, and they extend nearly a quarter of a mile along the shore. A little to the northeast of Nash's Point 

 in Shelburne is a similar deposit near the lake shore, and they are also exposed by ploughing at some 

 distance from the shore, where they appear to have been thrown into ridges by the waves, as if upon a beach. 

 On the west side of Shelburne Bay near the south end, at the foot of a precipice, there is a locality, where, 

 although the shells are not very abundant, the Saxicava rugosa predominates, which is not usual. 



The eastern extremity of Juniper Island abounds in marine shells of several species. In Burlington they 

 are found in at least half a dozen localities. In excavating for the Central Railroad north of the village, 

 a stratum abounding in Sanguinolaria fusca was passed about 50 feet below the surface of the plain, and 

 three-fourths of a mile northwest from this is the locality already mentioned, by the roadside opposite the 

 dwelling-house of Charles Adams, Esq., lying in a layer a few inches below the surface of the ground. 

 Another of these localities in Burlington is on the north side of Appletree Bay. The shells are found in 

 the bank, about 25 feet above the lake. 



In Colchester there are several interesting localities. One is on the south side of Colchester Point, near 

 the extremity. Here they are most plentiful about one foot below the natural surface of the ground, and 

 10 feet above the lake. Another locality, and on some accounts the most interesting I have met with, is 

 on the south side of Mallett's Bay. These are washed from a nearly perpendicular bank 25 feet high, upon 

 which the waters of the bay are making constant encroachments, and what gives them peculiar interest is 

 the circumstance that large numbers of them are either wholly or partially imbedded in claystones. At 

 Clay Point there is another important locality, not only on account of the great quantity and variety 

 of shells, but their fine state of preservation. The locality in this town two miles northeast of Mallett's 

 Bay, on the land of Mr. Joel Harris, has already been mentioned. 



The fossil shells found at all these several places are bivalve, and at most of them a large proportion 

 have their valves united, and not a few retain their epidermis entire ; which shows, without a doubt, that 

 they lived and died in the places where they are now found. 



" The thickest part of this formation is about 200 feet." 



It is not necessary to add a list of all the localities of shells that we have found in the State, as we have 

 proposed to do, because they are so numerous. It is sufiicient to say, that by digging into the earth at 

 almost any place below 200 feet above the level of Lake Champlain, they may be found. Every island in 

 Lake Champlain, which has any soil upon it, is particularly rich in these fossils. The finest locality that 

 we have visited in the State, is at an excavation for the Vermont and Canada Railroad, 150 feet above the 

 ocean, in the south part of the town of Swanton, near the house of Charles Bullard. 



BEDS OF MARL. 



Alluvial marl is usually a fine powder consisting of carbonate of lime, clay and soluble and insoluble 

 geine. Quantitative analysis shows, also, the presence of phosphate of lime, carbonate of magnesia and 



