CHAMPLAIN DIVISION. 419 
The following section in Galway, illustrates the Potsdam sandstone, and the base of the 
Calciferous group. 
FEET. INCHES. 
1. Argillaceous conglomerate. 1 2 
2. Limestone. 0 9 
3. Limestone, argillaceous. 0 9 
4. Gray siliceous hard sandstone. 40 0 
6. White ditto ditto . 2 0 
7. Grey ditto ditto . 25 0 
8. Cluartz . 10 0 
9. Siliceous fissile slate. 15 0 
10. Whitish quartzose sandstone. 8 0 
11. Sandstone (slaty). 6 0 
12. Sandstone (compact), unknown thickness. 
13. Primary rocks, gneiss, etc., unknown thickness. 
108 8 
The position of these rocks and their associates is indicated on Plate 28, fig. 1, where the 
Potsdam sandstone rests on the gneiss rocks, and the calciferous rocks upon the sandstone. 
It has been mentioned that the general dip of the Potsdam sandstone was to the east; but 
along the extremities of the southern spurs of the primary mountains in the southwest parts 
of Washington and Saratoga counties, the strata have a more general dip to the south. On 
the eastern side of these projecting spurs, the strata dip to the eastward; and on the western 
sides, they sometimes dip to the westward, and sometimes seem to plunge beneath the pri¬ 
mary rocks. 
Roofing Slate. 
This rock might, with propriety, it is believed, have been described under the head of Utica 
slate ; but it is an altered rock, intermediate in character (as are also its associates), between 
the rocks described under the Champlain division, and those to be described under the 
“Taconic system.” 
The roof slate ranges from Vermont, through Washington, Rensselaer, Columbia, Dutchess, 
Ulster and Orange counties, into New-Jersey and Pennsylvania, and is quarried for roof slate 
in many places. This rock and its associates, which are similar to those already described 
under the Champlain division, are penetrated by quartz veins in great numbers, and by inter¬ 
laminations of quartz, so that in many places the rocks seem permeated by this mineral as a 
sponge is filled with water, and this has given a modified character to the rocks. This cha¬ 
racter may be seen illustrated in the hills near Redrock village in Canaan and Austerlitz in 
53* 
