556 ISLE OF MAN. GEOLOGY. LIMESTONE. 



gularly intermixed with them, forming a portion of the 

 common deposit. Although it is here called unstratified, 

 on account of its predominant character, this feature ia 

 not always definite ; since it is found in certain places 

 to pass gradually from a shapeless mass into the form 

 of regular beds, and, in certain cases, may even be traced 

 into the ordinary stratified rock. 



It is commonly of a crystalline texture, often indeed 

 highly so, like some varieties of the primary limestones ; 

 the plates being of large size, and at times translucent 

 on the edges of the fracture. It is extremely refractory 

 under the hammer, and all these distinguishing charac- 

 teristics are most perfect where the semblance of stra- 

 tification is most completely wanting. Where it passes 

 into the stratified limestone, its mineral character also 

 undergoes a gradual alteration, until it ceases to be dis- 

 tinguishable from that variety. 



In colour, it displays nearly the same modifications 

 as the stratified limestone, with the exception of black, 

 of which no instance occurred during the investigation. 

 The paler greys seem to predominate, and in some partial 

 spots the rock even becomes of an impure white. This 

 circumstance is interesting, and is analogous to that 

 pointed out in Sky. If the unstratified is a portion of 

 the stratified rock, changed in character by some opera- 

 tions posterior to its deposition, it would hence appear 

 that the causes, whatever they may have been, have 

 also dissipated the bituminous matter from which the 

 colour is derived; as they also seem to have destroyed 

 the organization of the shells once imbedded in it. A 

 breccia consisting solely of different coloured fragments 

 of the same variety, and entirely different from those 

 formerly mentioned, is found connected with it near 

 the contact with the schist in the neighbourhood of 

 the Santon river. 



The unstratified limestone is often so changed, and 

 that to so great a depth from the surface, that its true 



