160 CHAMPLAIN CLAYS. 



at a much higher elevation than the fossils, and the continuity of the deposits leads us to 

 ascribe the same origin to all. This height is at Monkton Pond, where it is overlaid with 

 marl. It is near the " oven" also, and the clay may be found abundantly in the whole 

 region below the height of 756 feet. Thirdly, to ascertain, so far as possible, the altitude 

 of other beds of clay in other parts of the State; that by comparing heights, we may learn 

 whether a common marine origin may be ascribed to all. The highest beds of clay that 

 were measured, were in the valley of Lake Mcmphremagog, in West Derby ; the plain 

 upon which the village stands being its upper limit. This was 778 feet, only twenty feet 

 above the clay in Monkton. Others were found upon the Winooski at "VVaterbury, Mid- 

 dlesex, and Montpelier, the base of the latter being 540 feet above the ocean. On Con- 

 necticut Kiver we do not recollect any case higher than that at Newbury, which was 410 

 feet above the ocean. On White River, at Hartford, one is 500 feet high. Between the 

 altitudes of 410 and 150 feet, they are frequent between Newbury and the south line of the 

 State. These were the only examples whose altitude was taken ; nor did the propriety of 

 the thing strike us till after the close of the field work. It is very likely that others may 

 be found at a greater level. Other beds than these mentioned were frequent in Rutland 

 County. Fourthly, to learn what towns in various parts of the State would be submerged 

 at the various levels specified, viz : at the height of 325 feet, the highest point where the 

 shells are found in Vermont ; at the height of 520 feet, their upper limit in Canada ; and 

 at the height of the clays in western and eastern Vermont. 325 feet of elevation of 

 oceanic waters would submerge the greater part of Franklin, Chittenden and Addison 

 Counties, and the Connecticut River valley nearly to White River Junction ; 540 feet of 

 corresponding elevation would cover the three counties mentioned, with the greater part 

 of Rutland County, a large tract in Bennington County, and would extend up the Con- 

 necticut above Barnet. A depression of the country to the level of the clay beds, would 

 submerge a great part of the State, extending above Barnet on the Connecticut, above 

 Lyndon on the Passumpsic, above Montpelier and Northfield on the Winooski, above 

 Hardwick on the La Moille, and would cover up a part of the old sea bottoms east of the 

 Green Mountains, besides the territory covered by the waters at the lower elevations. 



One of the most important points discovered during the whole progress of the Survey 

 in reference to the Champlain clays, is that referred to by Prof. Adams in his division of 

 the whole into two parts characterized by their fossils. This distinction was mentioned in 

 his Report, but as it was not a final report, it is possible that he may have been aware of 

 its importance. The lowest division, or the blue clay, contains only shells that inhabit 

 deep water. The upper division, or the brown clay and the sands, contain littoral shells, 

 etc. Hence these two deposits were made under quite different circumstances the one in 

 deep, and the other in shallow water. And we shall notice subsequently the fact that the 

 oldest deposit was formed when the waters were at a greater depth, and that there is no 

 deposit of shells of any kind between the drift and the blue clay. 



I. THE BLUE CLAY. 



The blue clay is stiff, argillaceous, and sometimes much indurated. It is usually found 

 in the lowest grounds near the lake, and is rarely associated with other than clayey strata. 

 Sometimes the texture is very fine, and it forms then a fine clay for the manufacture of 



