162 
GEOLOGY OF THE SECOND DISTRICT. 
is the earthy black oxide of manganese, which also passes through the same changes as the 
preceding minerals. Even carbonate of iron is sometimes present, passing through this order 
of changes ; first, it is enclosed in fine particles in the impure limestone, which, decomposing, 
finds some hollow or basin that retains the matter, and prevents its transportation to the sea 
and other great reservoirs. When quietly deposited, a series of changes take place, which 
end with the perfect reunion of the particles in solid crystalline masses. In all these changes, 
no heat is required; a combination with water to give mobility to the particles, is all that is 
necessary. When the materials are partially soluble, we find a most perfect crystallization ; 
but even where the insolubility is great, as in the oxide of iron, we find that a state of mobi¬ 
lity results in a regular arrangement of the particles. 
That the preceding views are correct in relation to the origin of hematite, manganese, etc., 
appear quite probable, from the fact that these ores occur only in the Taconic system. We, 
in fact, never find them out of the belt of country traversed by these rocks. Thus it appears 
proper to place those products in this system of rocks ; they were originally a part of it, and 
subsequently, by decomposition and transportation, were removed to some other place within 
the bounds of these rocks. It will be observed, that though the products of this rock are few 
in number, they are still highly important, and worthy of careful investigation. At short 
intervals only, these products are carefully treasured up, for our use. We know the general 
range of the system, and knowing that it is within its bounds that these varieties of iron and 
manganese are to be found, we are furnished with a clue to their discovery. Probably these 
beds will be found extremely numerous ; it ought to be borne in mind, however, that they are 
by no means inexhaustible, and that they are accidental deposits, and that they may be en¬ 
tirely removed in process of time. 
Some of the hematitic beds furnish an excellent ore, or one suitable for the most perfect 
productions in this metal. It is an interesting fact, that New-York contains within her bounds 
four species of iron ore : 1st, the magnetic of the Primary ; 2d, the specular of the Primary 
also; 3d, the hematites of the Taconic system; and 4th, the argillaceous or oolitic of the 
Ontario group. Each of these ores occupy different geographical as well as geological posi¬ 
tions or relations. The two first belong to the original constitution of the earth, and the two 
last are formed from the decomposition of materials preexisting in another form or condition. 
To these species, we may add the bog ores of still more recent formations ; they are products 
of our own time. It is to be observed, too, that their distribution is extremely favorable to 
supply the wants of the inhabitants of New-York. The east, the south, the west, and north, 
have each their ores of iron. The highlands, which are broken and mountainous, furnish all 
the magnetic ores ; the hilly and moderately elevated, the hematites ; the rolling and swelling 
country of the west, the oolitic, or argillaceous. 
