1822.] Geology of Snowdon, and the surrounding Country. 325 
cibly attracted attention; namely, that the slate quarries of 
North Wales extend along a line bearing north-east and south- 
west from Aber to near the Pwhhelli (a fact we had no personal] 
opportunity to verify), and this information first drew our pecu- 
liar attention to the direction of the slaty cleavage, and which 
we rarely or never failed to notice afterwards. 
Moel Shabod, whose base descends to the Lake immediately 
below the Inn, may be described as a single mountain rising to 
the height of 2800 feet above the level of the sea. Its north- 
western foot may be said to touch the base of Snowdon beneath 
the pass of Llanberris. 
Our first ascent was up the northern side of the mountain, to 
its summit from the back of the Inn at Capel Curig, and in gene- 
ral terms, it may be said, that three rocks, at first sight differing 
considerably from each other, presented themselves to our notice 
in succession, each prevailing at different elevations. The 
lower third, or the base, as it may be termed, consisted chiefly 
of arock which is often so slightly granular that at first view it 
appears homogeneous: the middle region appeared to consist 
principally of slates, and the upper part of a rock which some- 
times has greatly the appearance of a greenstone, but manifestly 
partakes of the nature of those at the base. : 
A close inspection of the prevailing rocks of the lower third, 
or base, of the mountain, however, discovers, when assisted by 
the glass, that they are composed of a translucent substance, enve- 
loping very minute portions of a green matter, imparting to the 
grey colour of the rock a greenish tint, which is heightened to 
ereen by the addition of moisture: when reduced to small thin 
fragments, the transmitted light is green: in a large proportion 
of our specimens, no quartz nor any other substance appears to 
be imbedded, nor does any effervescence take place on exposing 
them to the action of muriatic acid: in others, however, of a 
larger grain, some effervescence occurs : in others again, small 
transparent crystalline particles are imbedded, which do not 
yield either to the knife or acid, and wkich we, therefore, consi- 
der to be felspar, being of a more lamellar structure than quartz ; 
the lower rock often contains imbedded masses of a much closer 
grain, and harder than the rock itself. These rocks yield easily 
to the knife, passing before it into a greyish powder, and their 
fracture is uneven and splintery : we consider them to consist 
of a species of steatite enclosing chlorite, and we are so inclined, 
not simply from their general aspect, but also from the nature of 
one rock with which they are associated near the base of the 
mountain, and opposite to the back of Capel Curig Inn, It 
perfectly resembles a steatite of a greenish or yellowish-green 
colour, probably from the more intimate dissemination of the 
chlorite through its mass ; for chlorite does not, as in the former 
rocks, appear in minute particles, as its partly weathered edges 
