^equally distrib%ited, but deposited upon parallel surfaces, or what is more 
likely, separated so to form such surfaces, dividing the whole mass into 
layers without courses, and layers with courses of different thickness 
in different quarries, and in different parts of the same quarry. A selec- 
tion, therefore, becomes necessary, for a block cut from a layer with 
courses, requires to be handled with care to prevent a separation of its 
parts, and if exposed to water and frost, the like result must sooner or 
'later take place. It is obvious that such stones cannot be used to ad- 
vantage where a durable structure is to be made, unless placed below 
-the point where ai-r and congelation have accesSr; and none but single 
•or unit masses ought to be used above that point, and of the greatest 
^dimensions; weight being of far more importance in our climate towards 
>making permanent works, than the best cement yet discovered. 
This limestone is hut a thin mass of from 8 to 12 feet in thickness. 
Above the gray limestone there is a series of shelly rotten layers of 
impure limestone, probably caused by an increase of the shaly matter of 
^1 he gray limestone, changing all the characters, chemical, mineral and 
fossil which belong to that rock» The total thickness of the layers is 
from 9 to 12 feet„ 
These layers in their turn are followed by another ^all series, con- 
^sisting of limestone, usually black, compact and rather brittle, generally 
4:erminated by one or two layers, containing nodules of Hint, the flint 
arranged in parallels. In some quarries there are no less than ten lay- 
ers or ranges of flint. With a change in composition, there is a change 
in the fossils likewise, which is common to all the New-York rocks, 
and to rocks elsewhere; a change of material denoting a change of circum- 
stances, which whilst they favor the increase of certain classes and spe- 
cies of organic beings, may be injurious to others. The layers below 
the flint, w^hrch I understand is the true cornitiferous rock," of Prof. 
Eaton, and are extensively worked at the different quarries to the north 
of Auburn, where the whole series may be seen from the upper part of 
the water lime group, to the layers which contain the flint. The whole 
disposed in two or more terraces which extend east and curve west and 
south towards Springport. The thickness of the last series from J5 to 
20 feet. 
Seneca Limeslone. This rests upon the layers of " cornitiferous," as 
may be seen at the falls of Oneida creek. This is the last connected 
series of the great limestone range; all the limestones which are found 
above the Seneca limestone, with the exception of the Tully limestone, 
