30 
SILUEIA. 
[Chap. II. 
These, then, are the only signs of former 
life we have yet become acquainted with, after 
the most assiduous researches in the Cambrian 
deposits of such vast dimensions, which are 
often, I repeat, less altered than much younger 
rocks replete with organic remains. 
Let us now mark the same first clear steps 
in the geological series of North "Wales, as 
worked out by the Geological Surveyors, and 
indicating a succession similar to that first de- 
scribed in Shropshire. 
In the well-known scene figured below, 
the spectator is supposed to be looking to 
the Pass of Llanberis, from the lower lake of fossil.) 
that name, the heights of Snowdon being in the distance on the right 
hand. In the foreground, and on both sides of the ruined castle of Dol- 
badarn, the faces of the cliffs exhibit flexures of the oldest strata here 
Pass of Llanberis, from the Loaver Lake. 
visible. These are the purplish and grey slaty rocks (No. 2 of the 
section at p. 24, and No. 1 of that at p. 26) whose structure and re- 
lations in North Wales have been so well described by Professor Sedg- 
wick. Containing the best roofing-slates in the world*, and subor- 
* The slates of Llanberis lie in the masses to on the N.N.E. A very instructive diagram, repre- 
the left hand of the foreground, and were the pro- senting the curves of the original strata at Llan- 
perty of the late Mr. T. Assheton Smith. Thence beris, and the manner in which they are traversed 
they range to the great quarries of Lord Penrhyn, by planes of slaty cleavage, is given by Professor 
Fossils (3). 
Oldhamia antiqua (E. 
Forbes), from Carrick Mac- 
Keilly, Ireland. 
(Eemains of Fucoids ? are 
occasionally found with this 
