TACONIC PHYSIOGRAPHY. 47 
THE LAKES AS RELATED TO ROCK STRUCTURE. 
Most of the lakes of this region (enumerated on p. 22) have little 
1 any relation to rock structure. Their presence was determined 
iither by the distribution of glacial deposits or by the silting of 
[flannels in such deposits. Others lie upon the rock in shallow 
epressions formed by erosion and in some cases dammed up on one 
r more sides by glacial deposits. Of such character are the Humer- 
us lakes on the Rensselaer Plateau, the lakes of Berkshire County, 
[pd most of those of the Hudson-Champlain valley. 
Lake Cossayuna, in Argyle, lies in a rocky basin, but the structure 
If its surrounding ledges furnishes no clew to its origin. It may be 
[art of the channel of an ancient river. Lake St. Catherine, in 
! pultney and Wells, is bounded on the west by a slate ridge and on 
IJhe east by a schist ridge. As the boundary between the two forma- 
[ions crosses the lake diagonally and the slate is probably anticlinal 
Iffi structure, the hollow in which it lies has been eroded. Lake 
i Bomoseen, in Castleton and Hubbardton, lies entirely in a region of 
I |mall folded slates, etc., which crop out along its shores. The gen- 
eral trend of the lake corresponds approximately to the strike of 
Ihe folds. But there is a cut through which the outlet of Glen Lake 
(flows into Lake Bomoseen, and the shore of Lake Bomoseen west of 
Cedar Point is in line with this cut. The parallelism of this cut 
ind this shore line to some of the joints, and also to a camptonite dike 
Ijvhich crosses the lake a mile north of Cedar Point, indicates struc- 
tural relations between them. In other respects this lake is to be 
attributed to erosion and to both glacial and stream deposits. Lake 
punmore, in Salisbury and Brandon, Vt. (PL XIII), seems to lie in 
a southward-pitching syncline of quartzite, with overlying dolomite, 
[the dolomite having been largely eroded. The valley at the northern 
uid of the lake is formed by this syncline. The damming up of the 
syncline at the south by Glacial or post-Glacial gravels may be the 
i-eason for the outlet of the lake not being in its natural place. Silver 
.Lake, 070 feet above Lake Dunmore, lies within a narrow syncline of 
dolomite underlain by quartzite (p. 43 and Pis. XIII and XIV). The 
deep transverse cut between Silver Lake and Moosalamoo crosses this 
syncline without having penetrated all of the dolomite. The lake is 
retained in its syncline by glacial gravels. Both of these lakes are 
thus associated with rock structure. 
CONCLUSION. 
The history of the Taconic landscape, from a geological point 
of view, is a long one. Its chief events, briefly summarized, were 
the accumulation in a broad arm of the ocean of arenaceous, 
argillaceous, and calcareous materials by erosion and by mechanical 
