CALCIFEROUS SANDROCK. 
105 
intensity of the forces by which they were transported. In some places, therefore, they are 
coarse, and irregularly mingled; in others, they are fine, but in large quantities, and appear 
to have been borne along by a moderate current, which has given a diversity in the stratifica¬ 
tion resembling that of inclined beds, or beds which have been elevated subsequent to their 
consolidation, as in the annexed diagram, fig. 33. Phenomena of this character are common 
to all accumulations of gravel and sand, bufdo not 
become evident in any of the argillaceous or calca¬ 
reous rocks, probably in consequence of the extreme 
fineness to which the particles are reduced. Among 
other phenomena, ripple marks may be seen through¬ 
out the whole of the rock, when the materials were 
not too coarse ; showing that during the period when 
this deposit'was in progress, the waters were quiet, 
and free from those disturbances which give origin 
to a confused stratification. 
Fossils. —The Potsdam sandstone is extremely poor in fossils ; but it is interesting to find 
even a single bivalve shell, thus setting aside the former crude notions in relation to the order 
in which beings were created. The only distinct and well characterized fossil of this rock, is 
the Lingula ovata, found abundantly at the High bridge near Keeseville. It is small, very 
thin, and rather obscure. It is also found in the same rock at French creek, about one mile 
east of the village, in a friable variety of the rock. Besides this fossil, another resembling 
the Fucoides demissus of Conrad, occurs between Wilna and and the Natural bridge in Jef¬ 
ferson county : it is not characteristic of the rock. 
2. Calciferous Sandrock. 
Mixture of earthy and calcareous matter. — Presence of Calcareous Spar. — Geodiferous. 
As its name indicates, it is a sandy limestone : it is not, however, destitute of beds of pure 
limestone. The mixture of a variety of mineral matter causes the rock to weather unequally; 
hence it is often rough externally, portions of the siliceous part standing out in relief. This 
rock is not uniform in its appearance, although there is in general a peculiarity which distin¬ 
guishes it from the other rocks of this group. There are two quite uniform characters which 
may be observed in the calciferous, viz. a fine crystalline structure, intermixed with earthy 
matter, and numerous small masses of calcareous spar. A section will best exhibit the usual 
order of the varieties which compose it, and which I have placed under this name. 
Geol. 2d. Dist. 
14 
