54 GEOLOGY OF THE SECOND DISTRICT. 



subject to igneous action, wliicli lias caused it to protrude in numerous instances among other 

 rocks of a recent date. 



There is another fact brought out by tlie relations of the rock at Tiieresa 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 ; fur 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 tlie position which this blue limestone 

 occupies. I am sensible thiit 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 connnon 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 hmestone 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 RoDOERs's Final Report of New-Jersey, p. 72, 



