IGNEOUS ORIGIN OF LIMESTONE. 



47 



of deposition obliterated, but new ones often appear, dividing the rock into innumerable 

 rhombic prisms, a form which had no existence in the mass at the time of its deposition. So 

 the sedimentary hmestones, being composed of the finest of abraded particles, combine under 

 the form of the species, producing thereby a crystalHne mass. The coarse materials of sand- 

 stone, however, never assume this crystalline arrangement ; and it is only those which are 

 composed of the finest particles, which occur in distinct angular masses, indicative of crys- 

 tallization on a large scale. Whatever may be the fact in relation to this matter, crystalline 

 masses do occur under circumstances in which igneous action seems not to have been the 

 agent ; tlius it is with the upper part of the Trenton limestone, which is a grey crystalline 

 mass, and beneath are dull black earthy strata, which being placed beneath, would be more 

 acted upon than those above. This structure does exist, then, without igneous action ; and 

 so long as the contrary cannot be proved, we have much reason for believing that the saccha- 

 rine hmestones and crystalline schists may also have been modified by the same cause, without 

 ignition. 







a. Lime.stone. 



b. Granite. 



Returning from this digression, to the subject of the origin of the primitive limestone of 

 St. Lawrence, I refer the reader to diagram No. 7, which, though it shows the same relation 

 of granite and limestone as the preceding cuts, yet presents some features not contained in 

 either of them. The slight wavy surface of the limestone is an arrangement of the materials 

 in a manner resembling gneiss, but still I am not disposed to consider it as stratification : it is 

 an appearance which I am unprepared to explain. The locality is Lyndhurst, in one of the 

 British Provinces. 



It will be perceived that the diagrams which I have selected for the illustration of the 

 origin of this variety of limestone, have been taken from a wide extent of country, which fact 

 favors the idea that the relations and phenomena which they illustrate are by no means local. 

 There is a sameness, however, running through the whole of them, and it is probable that it 

 may be thought unnecessary to multiply them to such an extent ; and were the question of 

 less importance and interest than it is, such a view of the subject would be just ; but as there 



