235 



Art. III. Outlines of Geology, being the Substance of a 

 Course of Lectures on that Subject, delivered in the Am- 

 phitheatre of the Royal Institution of Great Britain, by 

 William Thomas Brande, F.R.S., Professor of Chemis- 

 try in the Royal Institution, fyc. 



[Continued from page 40 of the present Volume.] 



VI. 



The transition limestone of the Wernerian school appears to be 

 the same with that usually called mountain limestone by English 

 geologists; it forms many hilly, rocky, and mountainous dis- 

 tricts, of singularly picturesque and romantic scenery in Britain ; 

 it is generally so compact in its texture as to break splintery — 

 it takes a good polish — its usual colours are black, bluish, and 

 reddish gray ; it is often beautifully traversed by veins of calcare- 

 ous spar, which give its surface in some instances a reticu- 

 lated appearance ; and it is in many parts characterized by its 

 abundance of organic remains, more especially by those of marine 

 animals, such as corallites and encrini. It is also rich in the 

 metals, and as already stated, is associated with our coal strata, 

 forming as it were the ground or basis upon which they lie ; its 

 usual geological position being under the red marl and above the 

 old red sandstone ; the latter rock, however, is by no means 

 always in its place, and instances are not wanting in which moun- 

 tain limestone lies upon slate ; but in that case it is very scanty 

 in organic remains, and differs otherwise in appearance from the 

 rock that lies upon the sandstone. I shall first briefly enumerate 

 the principal districts in Britain characterized by this formation, 

 and afterwards advert to its aspects and peculiarities as consti- 

 tuting mountain masses. 



The great patch of limestone extending from the Tweed to the 

 Tees, bounded by the coal measures on the east and by the Cheviot 

 Hills on the west, is commonly called the lead measures, in conse- 

 quence of the abundant veins of that metal by which it is tra- 

 versed. Indeed the rocks which we are now about to examine 



