No. 50.] 325 
those straight columnar masses which appear in the western Hmestone, 
which are produced by the crystalUzation of sulphate of magnesia or 
some other salt. Probably it is the lowest rock in which this appear- 
ance is known. 
Trenton Limestone. 
This is the most extensive rock in Jefferson county. It is the gray 
variety, interlaminated with seams of slate of a darker colour than the 
limestone. At the surface in many places, it is separated into innu- 
merable roundish pieces by weathering. I^hese are the hardest portions 
of the rock, and seem to have been produced by molecular atttraction, 
while the rock was in the progress of consolidation. It is generally 
loaded with organic remains, as several species of Orthoceras, Stropho- 
mena, Delthyris, Orthis, Lingul^, Belierophon, Isotelus, Asaphus, Caly- 
mense, Columnariae, Cyathophylum, &c. These genera constitute but 
a small part of the fossils which are found in the rock. 
This rock extends across the country from east to west, or from 
Champion to Sacket's-Harbor. It is especially well developed in 
"Watertown, Brownville and Sacket's-Harbor, Pillar Point, Adams and 
Rutland. 
It is not the repository of any metals, so far as is known in this coun- 
ty. It is, however, a valuable rock as a building stone in its rough 
state, and the compact and sound portions form valuable marble. It is 
an excellent substratum for soil. It not only furnishes the elements of 
a good soil, but one which produces a somewhat peculiar vegetation. 
Thus the neighborhood of Watertown produces many rare botanical 
species which are confined to those places underlaid by this lime- 
stone. 
This rock is remarkable for its cavernous structure. Several exten- 
sive caves occur in it, in the vicinity of Watertown and Brownville. 
These abound in beautiful stalagmites in which we frequently find the 
bones of bats. These subterranean passages were evidently formed by 
the action of running water. When these passages had been formed, 
much as we now find them, the percolation of water through the roof, con- 
taining in solution carbonate of lime, commenced, a portion of which fell 
on the limestone beneath and then accumulating, it slowly deposited the 
remaining carbonate of lime on the floor. The external forms of these 
concreted masses are various. Some are in crystalline nodules, others 
