Crystalline Limestone. 359 



that we do not, in fact, at all understand their nature, and that, 

 as these are so little adapted for investigation by the assistance 

 of experiment, there is but little prospect of afterwards ac- 

 quiring more than a conjectural knowledge of the subject. 

 The prospect is certainly not enticing. We have, however, 

 acknowledged that it is quite natural that a complete and per- 

 fectly candid study of facts must often leave us with nothing 

 but what is inexplicable. If it be true that, when every thing 

 is fully explained, there is room for doubting that the strictest 

 attention has been paid to what is matter of fact, the friend 

 of truth will readily be satisfied with his less distinct result. 



We now proceed, so far as that can here be done, to treat 

 of the marble which occurs in the oldest rocks, or in forma- 

 tions which contain no organic remains. I say, in so far as 

 that can here be done, because our opinion of the origin of this 

 marble is, after all, entirely dependent on the view we deem 

 it necessary to take of the mode of formation of the principal 

 rocks among which it presents itself. 



Here in the North — and, no doubt, the same is the case in 

 other places — what is termed primitive limestone occurs most 

 frequently in gneiss, mica-slate, and hornblende-slate, in masses 

 which, at the first glance, might be thought to have completely 

 the nature of beds, but which, on closer inspection, do not at all 

 correspond entirely with the idea of beds, in so far as we un- 

 derstand by the term bed a particular stratum constituting a 

 member of a series of layers parallel to one another, which were 

 gradually deposited the one upon the other, each for itself in its 

 own period of time. The relations exhibited by these masses 

 of marble are by no means so simple as they would have been, 

 had, for example, a stratum of mica-slate been first formed, 

 then over it a stratum of marble, and again over the last mica- 

 slate. It is not only the case that, at the junction of the lime- 

 stone and the including rock, we find both masses, as it were, 

 mixed with one another, inasmuch as frequently grains of calc- 

 spar are disseminated through the slate, and in the same way 

 the constituents of the latter disseminated in the marble, but 

 both rocks frequently invade the boundaries of each other in 

 a bifurcate manner ; nay, portions of slate, entirely isolated, 

 are often met with embedded in the marble, while the latter 



