Connecticut River Valley. 223 
of water, may also have assisted. Most of the strata in which clay 
largely predominates, though hard in their natural beds, decompose ra- 
pidly and return to clay, when exposed upon the surface of the ground. 
Overlying clay.—The formation of secondary rocks seems to have 
ceased, before the supply and subsidence of materials was discontinu- 
ed. Over the clay rock in Hartford, Windsor, Suffield and many 
other places, is a covering, often from ten to twenty feet thick, con- 
sisting of uncemented clay, exactly resembling in color and fineness, 
the substance of decomposed clay rock. These overlying beds of 
clay preserve no traces of arrangement in plates or layers. They 
also contain large pebbles and fragments of granite, greenstone, and 
other rocks, contrary to the invariably fine composition of the clay 
rock layers beneath. Such beds of clay are penetrated in the ex- 
cavation of wells in Hartford and other towns, and have been ex- 
tensively laid open, along the banks of the river at Enfield falls. 
Besides imbedded pebbles and fragments, the upper strata of the 
clay rock are found dislocated and mingled with the overlying clay. 
The broken masses having been lifted and imbedded, were left incli- 
ned in all directions, but are capable of being restored to their origin- 
al position, by bringing together their dislocated joints, which remain 
as perfect as in layers recently broken. 
Lake of the secondary formation.—Was it a fresh-water lake, or 
a bay from the ocean, which anciently overflowed the bed of the 
secondary formation? ‘The absence of remains of marine productions 
indicate the former, and that the Jake was little, if at all, open to the 
influx of tides. Jt could hardly have been a bay from the same pro- 
lific ocean in which were formed the vast beds of limestone and shells 
that extend from the Hudson river westward. 
Ouilet of the lake.—If it was a lake, the barrier which upheld its 
waters must have been since removed ; and the outlet was probably 
im the direction of New Haven. - If the present opening in the course 
of the river, from Middletown to Long Island Sound, had existed, 
the lake must have flowed into or through it, and it becomes difficult 
to account for the entire absence of secondary rock, in that direction. 
Change of elevation and dip of the secondary.—It has been already 
remarked that the lake or bay must have been at least coextensive 
with the secondary formation. It may be added that, unless great 
changes in the-elevation of the sandstone have taken place since it 
was deposited and formed, the lake must have extended far beyond 
the limits of the remaining secondary rock. A lake high enough to 
