Remarks ‘on the Transition Rocks of Werner 28 
ynost remote corners of the peninsula. On examination, I 
think they will be found sufficiently similar to the grau- 
wacke of Werner, to be entitled to be classed along with 
that rock. Dr. Berger, in bis paper on the physical struce 
ture of Cornwall, gives them no other name ; and if autho- 
rity is to be qualified by experience, the opinion of one 
who has traced the footsteps of Saussure, and who has 
Studied the geognosy of Werner with the utmost en- 
thusiasm, cannot fail to be received with respect. 
I have thus endeavoured to show by the selection of spe- 
cimens, and by the opinion of a very scientific observer, 
that the stratified rock of Cornwall is grauwacke. It would 
be uncandid, however, not to acknowledge, that the general 
texture of this rock was different from the grauwacke of 
the south of Scotland; it was more of the slaty variety, 
and frequently seemed, from its smooth and soft feel, to 
contain a large proportion of magnesian earth *, / 
I understand, that in a course of lectures now delivering, 
a very material alteration has been proposed upon the Wer- 
nerian system, in order to introduce this rock in a position 
distinct, and very distant from grauwacke. It appears to 
me much more simple to suppose, that rocks of the same 
class, in different districts, may present peculiar characters, 
than that the operations of nature should have been so 
multiplied and complicated, as to afford the endless distinc- 
tions which are thus required. Indeed, I cannot help 
thinking, that if the killas of Cornwall had been sufficiently 
known, it would have excluded entirely the introduction of 
that harsh-sounding German term Grauwacke. Killas ap- 
pears to me to be as proper a translation of that word as 
Specolar [ron-ore is of Eisen-glanz, and | think may be 
used with great propriety; distinguishing grauwacke and 
grauwacke-slate, by amorphous and schistose killas. 
The only other rock of any importance in Cornwall is 
granite, termed Growan by the common people,—a name 
also given to clay-porphyry, a substance found pretty fre- 
quently in large veins (Nos. 16 to 19, 28, 48.}. The shades 
of distinction chronicled by the mineralogist cannot be 
expected Lo attract the attention of the miner, who knows 
but two rocks, growan and killas, throughout the Stan- 
naries, It has been thought that a distinct rock was un 
* Since I read this paper, I have had occasion to pass through the trans- 
ition country of Peeblesshire, &c. On former occasions, | was in the habit 
of searching for characteristic specimens of the grauwacke ; I now looked 
for such as ressembled the killas of Cornwall, which I found in abundance 
(Nos. 62, 63). 
B4 derstood 
