54 
GEOLOGV OF THE SECOND DISTRICT. 
subject to igneous action, which has caused it to protrude in numerous instances among other 
rocks of a recent date. 
There is another fact brought out by the relations of the rock at Theresa falls, besides the 
one I have just considered : It is this, that the coarse crystalline limestone beneath the sand¬ 
stone is not the blue limestone described in Prof. Rodgers’s Report, from which extracts have 
been made.* In all localities, that limestone is above the sandstone ; and although it should 
appear that this blue limestone of the New-Jersey Report is truly an altered rock, and that 
all the facts and phenomena are as stated in the report, yet it does not affect the state and 
relation of the rock at Theresa; for the position of the mass here is perfectly plain, and no 
possible change can be conceived by which those relations could ever have differed: the 
crystalline mass can, by no hypothesis, be placed in the position which this blue limestone 
occupies. I am sensible that it was scarcely necessary to have presented this view of the 
subject; the inference is so plain, that few, if any, would probably entertain the idea for a 
moment, that this mass could possibly be the transition rock referred to; but so common and 
so popular are those views which represent strata, and even mountains, as overturned, that on 
every possible occasion they seem to be brought up, and from their astounding character, are 
fondly entertained, without inquiring whether some other more simple explanation may not be 
offered, equally satisfactory, and equally agreeable to the facts of the case. 
The fact that calcareous spar is the common gangue of metallic veins, is important in the 
decision of this question. Probably limestone is one of the most constant substances in 
mineral veins. All the lead and copper mines of St. Lawrence contain abundance of this 
mineral. I would not assume the point that veins are of igneous origin, though I think there 
are very few reasons for the contrary opinion; for the electro-magnetic theory is incompetent 
to satisfy the requirements of these facts. The fact, however, being proved, that limestone is 
of igneous origin, it goes far towards establishing the filling of veins from below. 
Proofs of the igneous origin of limestone, drawn from its imbedded minerals. 
Few rocks are so productive in the simple minerals, as primitive limestone. First, we may 
notice their mode of occurrence, which is probably the fact of the most consequence; thus, 
they are perfectly disseminated through the mass. Scapolite, pyroxene, hornblende and mica, 
though they are much more abundant at some particular places than others, still they do not 
occur in veins ; and such is their distribution, and the phenomena accompanying their pre¬ 
sence, that no doubt can exist of their being coeval with the rock itself. Their presence, and 
their condition or relation to the rock itself, differ in no respect from the occurrence of the 
same minerals in granite. In lava, in greenstone, and especially in that variety of greenstone 
called amygdaloid, the minerals are evidently posterior in their formation to the rock ; filling 
or occupying the- pores and cavities which are formed by the fusion of the materials compos- 
* See Rodgers’s Final Report of New-Jersey, p. 72, 73. 
