135 



The Lis/i Naturalist. 



elusion, viz., that the dolomites of this district, iiistead of beifig 

 superinduced structures^ are the remnants of sedime7itary 7vcks of 

 the Permian formation, resti^ig 2cnconformably on the denuded, 

 fissured, and excavated limestone. 



The principal grounds on which this opinion is based are as 

 follows : — 



1. The dolomitic bands which have come under my notice 

 have a general east and west direction ; this is such an 

 evident fact, that it has been customarj^, in connection with the 

 magnesia manufacture, to search for the rock in a direct line 

 east or west of the points at which it had been previously found. 



2. These deposits invariably show at the top surface of 

 the rock-formation, either overlying the limestone, or being 

 wedged in between masses of that rock which also show at 

 the surface on either side of them. 



3. Though in many cases the}^ penetrate the limestone for 

 a considerable depth, there is a general diminution of breadth 

 downwards, the horizontal section meanwhile widening or 



Figure i, a shows the 



narrowing in an irregular manner. 



Txa 1 





trf. 



plan, or horizontal section; fg. 2, the longitudinal section; 

 andfo; 3, the cross section of a small quarry which was 



