7; 
Notes on American Geology. _ 249 
tinctly, that it is very easy to estimate the comparative force of — 
currents on different strata by the larger or smaller undulations 
they have left behind. One can form an idea of the extent of 
one of these aricient floors of the ocean, when he sees the tipple 
marks, the same rock in mineral composition, and the same or- 
ganic remains in Germany or Wales that he finds in New York ; 
and can imagine how mighty a revolution the crust of the globe 
must have undergone to gain the vast depth of the Atlnatie and 
the elevation of the Andes. ~ 
While on the subject of ‘the transition; it may be nseful to in- 
quire into the relative position of a eabdotone which seems at 
present little understood. It appears on the Hudson, near New- 
burg, and passes under the Palisadoes, reappears in New Jersey 
and Pennsylvania, following the course of the Delaware a dis- 
tance of many miles, and disappears near Trenton; in New Jer- 
sey, where it rests unconformably-upon gneiss. The color of 
this rock i is generallyred, very often with pale waved and con- ~ 
centric stripes ; organic remains are very rare, one or two species’ 
of fucoids being all that I could find, and>they differ from those — 
of any other formation. 'This sandstone has sometimes been con- 
- founded with that of Western New York,-a gross error, arising 
from its general resemblance to'the latter. _Mr. M’Clure regards 
it as a distinct formation, but. terms it old red sandstone. It ap- 
pears to me to be. intimately connected “with the Hudson’ river 
slaty graywacke, probably one passing into the other ; but at all 
events it alternates with Eaton’s calciferons sandrock near Easton, 
a character which identifies it at once with the Potsdam and Es- 
Sex sandstone, described by Professor Emmons as occurring in 
the northeastern séction of New York. - In all cases it rests upon 
primary rocks cand is. the oldest of the fossilliferous formations, 
being under the calciferous sandrock,. and occupying - the same 
position in the geological series as the Cambrian system of Wales, 
described by Mr. Sedgwick. The copper mines of Flemington, 
in New Jersey, belong to this formation. ‘The harder layers 
make excellent building stone, and of this rock the Penitentiary 
near Trenton is constructed. In New York it is one of the most 
common materials for door steps and “basements, .and it is occa- 
_ sionally used as a building material in ringers where iti is 
brought down the Schuylkill river. 
Vou. XXXV.—No..2. 32 
