446 Dr. Mac Culloch on the Geology of 



the most musical, but we are not justified in changing them for so 

 slight a convenience. The late introduction of a new chemical 

 nomenclature, has possibly, in conjunction with other causes, 

 excited a taste for neology, which it behoves us to restrain by every 

 method in our power, and it is the duty of our Society to watch 

 over and protect the science from those changes which will, if not 

 restrained, shortly inundate us with as many names as we have 

 writers. 



The word killas^ a vernacular and Cornish term, has been proposed 

 as a substitute for graywacke. If killas were actually graywacke, 

 we might have a fair plea for using the name given to it by a 

 Cornish miner, in lieu of the corresponding one of a German miner. 

 But this is not the fact, as those who are conversant with Cornish 

 terms, well know that killas is applied to all the soft and fissile rocks 

 occurring in Cornwall, whether clay slate, or graywacke slate ; 

 and that it is never used for either when they acquire the more 

 compact and laminated form of roofing slate, a term as commonly 

 applied to this variety in that county, as in other parts of England. 

 The harder and more granular graywacke, is also called elvan, in 

 .common with trap, and other hard and dark blue stones. 



Aherfoyky 



Tt is well known that the ridge of which Ben Lomond forms a 

 part, consists of micaceous schistus,* which terminates near Drymen 

 in the highly elevated range of breccia that separates the primitive 

 from the secondary country, and which may be traced from this 



* In the Mineralogy of the Scottish isles, it is said that the summit of Ben Lomond 

 consists of gneiss. It is necessary to correct this oversight, tlie whole of the mountain 

 being formed of micaceous schistus, and no gneiss occurring in the neighbourhood. 



