100 
[AssbmblV 
The waters which drain the western and northwestern slopes, # 
are the Oswegatchie, Grass, Racket, St. Regis and Sahnon rivers. 
The first originates on the southwestern and the last on the north- 
ern slope, showing in the former case the commencement of a 
more elevated region as the chain proceeds north; the latter indi- 
cates a falling off of the same ridge as it progresses in the same 
direction. The southern and eastern declivities of this water- ^ 
shed are drained by the Hudson, Black and Au Sable rivers, .^gi^ 
The first and last interlock at their sources, and flow through deep 
gorges which have been formed, in part by the wearing action of 
their own waters, but more by convulsions in former times, which 
have rent and separated the rocky strata. 
From these observations, it appears that this high table land at- 
tains its greatest elevation near the sources of the Hudson and Au 
Sable rivers, and that it falls on all sides to about a mean level, 
but little higher than the ocean, in comparatively short distances. 
On the east, towards Lake Champlain, the descent is much more 
rapid than on the north-west, towards the St. Lawrence. Indeed, 
a traveller is entirely deceived in passing from the latter river to 
the Champlain over this tract: he cannot conceive that the general 
level is 16 or 1,700 feet above the level of the ocean, so gradual 
and imperceptible is the rise. 
It appears further, that in this region we have one single central 
ridge, to which all the other ridges are subordinate. It, in fact, 
forms the nucleus of this district, an important fact to be kept in 
mind in studying its geological structure. But little information 
can be given of the lower ranges, only, that they are parallel to 
the principal, and have a stratafication which conforms itself to that. 
We have already remarked, that Whiteface is generally consi- 
dered the highest of these mountains. Its height is stated at 2,600 
feet, while Roundtop, of the Catskiil, is 3,804, making the latter 
1,200 feet higher than the former. Suspecting previous to our visit 
to Whiteface, that there was an error in this statement of its 
height, and that probably it attained a greater elevation than had 
been credited to it, we made arrangements for its measurement. 
That our observations might be made under the most favorable 
circumstances, we determined to visit it on the 20th and 21st of 
September, as on those days* hourly observations are made on the 
* These observations are made on the 2l8t and 22d- 
