118 
[Assembly 
ing this rock in the manufacture of glass, it is first burned, then 
pulverized and washed. By long burning, or exposure to intense 
heat, it will become perfectly white, and free from any coloring 
matter. 
This rock frequently imparts to the country where it occurs, a 
curious aspect. Walls like regular mason-work may be seen run- 
ning with great regularity i or ^ a mile. Sometimes two walls of 
this kind remain, and run nearly parallel with each other. In this 
case, it appears that the intermediate portion has been entirely 
swept away. The upper surface of this rock is always smooth 
and polished, and sometimes grooved by what are termed diluvial 
scratches. Their direction at Hammond is nearly north and south. 
That this smoothness is owing to a wearing action of something 
which has slid over it, appears from the fact, that on clearing up 
a new layer the under surface is rough and harsh. Its organic re- 
lics have not yet been investigated. There are, in fact, very few 
in the rock. Potsdam, Hammond, and Theresa, are places where 
this rock may be examined, and where all the phenomena it pre- 
sents are exhibited. At Potsdam it might be mistaken for the old 
red sandstone. 
The soil reposing on this rock is not wanting in fertility. It is 
interesting to observe its productive qualities, when it is hardly 
more than a foot in thickness — even so thin that it would be per- 
fectly easy to turn a furrow in ploughing entirely from the rock. 
Those places where the soil is so extremely thin do not appear to 
suffer from drought. Vegetation is as fresh on them as where the 
soil is thicker. The cause of this is obvious. The rock is a good 
conductor of caloric, like all the siliceous stones; it therefore con- 
denses the water of the atmosphere, and preserves a degree of 
moisture; besides, the country is level, and the rains do not pass 
off very rapidly. 
As it is not our intention to describe this rock in full, or draw 
an exact outline of its extent, it will be sufficient for our present 
purpose to say, that its eastern margin is about 30 miles from the 
St. Lawrence, and that the line of this margin runs nearly paral- 
lel to it. Opposite the Thousand islands, it does not extend more 
than 20 miles east of the river. A traveller starting from Theresa 
Falls, for Hopkinton, might pass nearly along this margin. At 
the latter place it bears to the east, and takes a sweep round to the 
