412 Dr. Mac Culloch on the Geology of 



merely nugatory, but injurious to correct observation, chaining 

 down our conclusions in an obedience to particular dogmas, and 

 producing impediments destructive to the progress of legitimate 

 science. 



Another tract of limestone, of a distinct character, occurs in the 

 same valley, occupying a position nearly parallel, at some distance 

 from it. Of this I have unfortunately nothing to record beyond 

 the detail of specimens. The whole inclination of the hill on this 

 side of the valley is covered with a deep bed of soil, such as to 

 render it impossible to trace the position of the rock, of which, all 

 that is visible appears in the form of detached masses, apparently 

 without order or semblance of stratification, rising through the grass. 



The rock itself is an object worthy of attention from its oecono- 

 mical qualities, affording various specimens of marble, of a colour 

 from pure white to grey, which have already been introduced into 

 commerce, and for which a premium has been assigned to Mr., 

 Joplin, of Gateshead, from the Society of Arts. It is the same 

 marble described by Williams. The principal varieties are the 

 following : 



1. Pure white of a milky opaque aspect, with a crystalline tex- 

 ture, and large grained granular fracture, approaching to the splin- 

 tery. Acquires a smooth surface on the polisher, but remains of a 

 dead hue like the marble of lona, reflecting no light. Hence its 

 uses as an ornamental marble are much circumscribed. 



2. White mottled with gray, of a large platy fracture, and 

 capable of receiving a high polish, forming a marble of some 

 beauty. 



3. Highly crystalline and translucent, with a large platy fracture, 

 and of a gray colour, capable of being applied to the purposes of 

 43rnament in sepulchral sculpture. 



