222 Connecticut River Valley. 
Distribution of coarse and fine matertals.—In the lake or bay sup- 
posed, the heavier fragments and pebbles, brought within its limits by 
successive freshets, and by long continued currents, would subside 
near the borders. ‘The finer materials, sand, clay, &c. would be dif- 
fused, by the force of floods and currents, and the agitation of winds 
and waves, and gradually subside, in the order required by the laws of 
gravitation. Successive supplies of similar materials, driven by like 
currents and commotion of the lake into the same positions, subsided 
in similar order, and formed the plates, which, by repetition, complete 
a layer. Whenever a deficiency of cement occurred, or some un- 
cohering substance was diffused and subsided upon any portion of the 
previously formed strata, the subsequent deposit failed to unite with 
that which preceded, and separation into layers was the consequence. 
Of the alternations of sand and clay rock.—In many localities the 
layers are composed principally of sand, which being heavier than 
clay, subsided, and separated from the latter, wherever the currents 
which had borne the materials promiscuously into the lake, became 
sufficiently diminished. Other extensive, and generally central local- 
ities contain layers composed chiefly of clay, which was suspended lon- 
ger and floated farther into the lake than sand, and coarser materials. 
A layer of sandstone is sometimes interposed between layers of clay 
rock. These were, doubtless, products of currents and agitation in 
the water differing in violence, as we see them now in different years 
and seasons. With smaller floods and less powerful currents, the 
suspended sand was deposited nearer to the margin of the common 
reservoir, but was driven farther into the lake whenever violent currents 
prevailed, and subsided where beds of clay had been previously de- 
posited, thus producing alternate strata of sand and clay rock. 
Of color.—The color of the secondary formation, which is light red, 
in the coarser sandstone, and dark red or brown, and to a limited 
extent, deep blue or black in the clay rocks, was doubtless a product 
of iron ores, diffused in a state of minute division, inthe lake. ‘The 
fine materials of future rock, would both remain longer suspended in 
contact with the coloring matter, and present more frequent surfaces, 
to which the latter might adhere. Hence the darker color of the 
finer rocks. 
Cement.—Lime is found crystallized in the seams of many layers, 
and was probably the chief cementing subtance of the secondary for- 
mation. The iron of the coloring matter might contribute to strength- 
en the cement. Long continued and great pressure, by the weight 
