342 
GEOLOGY OF THE SECOND DISTRICT. 
been deposited from an aqueous solution, in beds or strata between the potsdam sandstone and 
the primary. 
Since the remarks in the early part of this volume were penned, the printed sheets of Mr. 
Vanuxem’s report have been placed before me ; and inasmuch as this gentleman’s views differ 
from my own upon the subject of the origin and position of the specular ores, I deem it but 
right that I should also place them before the reader of this volume. I shall therefore copy 
one or two paragraphs detailing his views : 
“ Specular ore is found in several places, associated with highly crystalline limestone. It 
“ exists near Lewisburgh furnace on the land of Mr. Lafarge near Harrisville, and in localities 
“ adjoining which belong to the Second district. When first discovered, there appeared to 
“ be a promise of abundance, but soon the spot was exhausted. It seems to have separated 
“ from the limestone by crystalline action, like gypsum and other minerals, being frequently 
“ enveloped in limestone. Where found, it is but a superficial mass ; and though its matrix 
“ is mixed with primary rock, the origin of the two was subsequent to that rock, appearing 
“ to have been local deposits of calcareous marl and oxide of iron similar to those met with 
“ in the gypseous region; the marl and oxide separating from each other by crystallization, 
“ being placed in a position which facts elsewhere prove was highly favorable to this opera- 
“ tion. That a deposit of iron was made upon the pri7na7'y rocks subsequent to their eleva- 
“ tion and alteration of swface, is evident from the third deqjosit of iron ore, wliich, near 
“ Lewisburgh furnace and in St. Lawrence county, is under the potsdam sandstone, in places 
“ intermixing with the base or lower part of that rock ; showing also at Lewisburgh the same 
“ limestone and specular ore, the supposed associates of the primary rocks, intermixed with 
“ red ore ; and thus proving a connection with the potsdam, as intimate, if not more so, than 
“ could be discovered for the primary massT * 
In the preceding paragraph, I have italicized those expressions which I wish the reader to 
notice more particularly. The fact as stated in relation to the thinness of the ore at Lewis¬ 
burgh, coincides with what I have elsewliere observed, and goes to show that my remarks in 
the early part of the volume, enjoining caution in incurring expense for the purpose of smelt¬ 
ing this ore, were well founded. 
The first point, on which I propose to speak briefly, is the opinion of my friend and asso¬ 
ciate, that the iron is a local deposit along with calcareous marl, analogous to the gypsum in 
the calcareous rocks. This of course is founded on the assumption that the platform upon 
which the specular oxide and limestone were deposited was the primary system; in other 
words, a sedimentary deposit, local in its origin like tufas and marls of any period. But 
what are the facts ? We find, in the first place, the same mineral, with the same associates, 
in veins traversing gneiss with all the regularity of veins of lead or trap dyke. When this 
substance therefore occurs under this form, there is little probability that it is an aqueous or 
sedimentary deposit from above — an infiltration. Again, the calcareous rock associated with 
Vanuxeii. Report upon the Geology of the Third District, p. 267. 
