18 Remarks on the Transition Rocks of Werner. 
wacke, and grauwacke-slate, trap and flinty-slate. Limes 
stone is placed first, as being the oldest member, and is 
said to rest immediately on the newer elay-slate*. Of this 
we have no instance which I am acquainted with in Scot- 
land, where, indeed, transition-limestone may be considered 
as rather of rare occurrence. Grauwacke and grauwacke- 
slate are with us the principal members. he first of these 
is a stone usually of a blueish colour, passing into gray, and 
sometimes grayish-red ; it is composed of fragments, often 
of considerable size, but sometimes so minute as to be 
scarcely distinguishable ; these fragments are quartz, clay- 
slate, flinty-slate, and occasionally jasper, which are agelu- 
tinated by a basis of clay-slate, through which minute par- 
ticles of mica are also sometimes dispersed. 
Grauwacke-slate differs from the fine-grained granwacke 
only in its minute stratification and fissrle character; it 
bears so strong a resemblance to clay-slate in hand-speci- 
mens, that even an experienced eye cannot distinguish it ; 
in the rock it is not so easily mistaken: it usually alternates 
with grauwacke, and is often remarkably contorted. Both 
substances are traversed by quartz veins, which are some- 
times of enormous dimensions, but generally very minute 
and abundant. 
The only limestones of this class that I know of are 
three: First, that of Rae Quarry, near Crook in Peebles- 
shire, where it is mterstratified with grauwacke, and con- 
tains abundance of shells. The second is that of Cumber- 
land, on the lakes of Windermere and Coniston, which also 
contains organised bodies. The third is the Plymouth 
limestone, which, according to the account of Professor 
Playfair, corroborated by Dr. Berger, is also transition- 
limestone; and in it Mr. Playfair states that he found a 
petrified shell +. ‘I have not myself visited the spot; but it 
is of consequence to observe, that the limestones of all 
. these diferent districts exhibit traces of organie remains. 
The other transition-rocks are trap and flinty-slatet; but 
I bave had no opportunity of observing either of them in 
their natural position. Such, according to Werner, is the 
extent of the transition series; but it does not comprehend 
all the rocks which occur in some of the transition districts, 
particularly that of Cumberland, although, with little ex- 
ception, it is adapted to the south of Scotland in a very 
remarkable manner. 
* Jameson’s Mineralogy, vol. iii. p. 147. 
+ Illustrations of the Huttonian Theory, p. 165. 
$ Isuspect both these abound in the mountains of Cumberland, from spe-~ 
cimens I have picked up among the loose fragments, 
(>) ‘ I may 
