Crystalline Limestone, J361 



geologist expresses himself in the following terms : — *' This 

 rock occurs in not a few localities under circumstances which 

 are in favour of its having hurst forth from the interior of the 

 earth in a melted condition, and that subsequently to the for- 

 mation of the gneiss and mica-slate. The limestone masses 

 bear completely the stamp of great veins, or of the upfiUings 

 of fissures. There are appearances indicative of a violent 

 pushing of the limestone into the surrounding rock. Where 

 the limestone is in contact with the bounding rocks, we find, 

 sometimes on the former, sometimes on the latter, the conse- 

 quences of powerful rubbings, exhibited in specular or friction 

 surfaces. Farther, the granular limestone includes fragments 

 and large masses of the bounding rock ; and lastly, where the 

 former meets other rocks, we find contact products of various 

 descriptions, according to the nature of the different rocks 

 which are in proximity to the limestone.'* 



Regarding the preceding quotation I must remark, that what 

 I have said of the mode of occurrence of the marble, may very 

 easily be made analogous to the appearances described by the 

 author. When the strata of the slate are much undulated and 

 contorted (as may every where be observed, both when the 

 marble is present and when it is absent), the whole pheno- 

 menon acquires a complicated aspect, and the isolated por- 

 tions of slate embedded in the marble may easily be thought 

 to resemble actual fragments, which, it may be imagined, 

 were violently torn from the hanging or lying sides. The 

 minerals disseminated in the limestone at its junction with 

 the slate, and which are the same as those of which the slate 

 is composed, may readily be taken for " contact products ;" 

 that is, for products of quite a different act of formation from 

 that which gave rise to the mineral species of the slates. 

 As to the marks of rubbing and sliding, they prove nothing 

 for the view expressed, as they can scarcely have been pro- 

 duced in any other way than by the action of perfectly com- 

 pact masses on one another ; and they are met with in all 

 places and in all kinds of rocks where separations have occur- 

 red, and where the separated part has been subjected to a 

 sliding or other movement. 



VOL. XXXVI. NO. LXXII. APRIL 1844. 2 A 



