Maw—Pochets in Mountain-limestone. 203 
When I first examined the deposit, I was under the impression, 
from their close resemblance to some of the clays and sands of Dor- 
setshire, that they might be outliers of Eocene age; and Mr. Prest- 
wich, who kindly examined some specimens I sent him, suggested, 
without expressing any decided opinion as to their age, that they 
could also be matched by some of the Lower Greensand strata of 
Surrey. Within the last few days I have more carefully examined 
the district, and ascertained the existence, on the Great Orme’s 
Head, of what appears to be another member of the deposit, which, 
in connection with the Nant-y-Gamer beds, may possibly afford, by 
comparison with other formations, a clue to their age, although at 
present the evidence of organic remains, or of superposition, is 
unfortunately wanting 
On the north-east side of the Great Orme’s Head a valley inter- 
sects the hill at a little beyond Llandudno Pier, and widening as it 
ascends, terminates with a broad end at Gwydfyd Farm (see Section 
fig. 2), against an abrupt precipice of Mountain-limestone. At the 
foot of this, a triangular space of several acres in extent, less steep 
than the lower part of the ravine, has afforded a lodgement for 
a deposit, resembling in colour the Nant-y-Gamer clays, but com- - 
posed of chert, intermixed with a little light-buff marl. On washing 
a portion of it, I find three-fourths of it to be made up of chert- 
fragments of various sizes, and the remainder of the sandy marl. 
Although no banded structure or stratification is evident, it has 
the appearance of being zm sifu, and not a drift. It is quite free 
from fragments of limestone or any other foreign matter; and is 
evidently the remnant of a once more extensive deposit, from which 
the chert fragments in the bottom of the Boulder-clay at Orme’s 
Bay was derived. 
It appears to entirely occupy the head of the valley at Gwydfyd, 
as chert is ploughed up all over the arable ground below the Farm- 
buildings; and the terrace-like form of the space it occupies, which 
is easily distinguishable at the head of the valley from a distance, 
clearly defines its range. 
Its full depth has never been ascertained; but as the face of the 
quarry above the Farm-yard, where it has been dug as gravel, is 
more than 20 feet, and as it was further sunk through near the 
buildings ten yards without the bottom being reached, a thickness 
of at least 50 feet seems probable. Its height above the sea ranges 
from about 250 to 350 feet. At about 100 yards to the north of 
the Farm-buildings a bed of buff loamy sand occurs by the road- 
side, which apparently overlies the chert-deposit and is probably 
connected with it. 
A careful examination of the district would probably display a 
further distribution of the deposit. At Bodafon, N.E. of Nant-y- 
Gamer, white sand and clay were found in cutting a drain; and I 
noticed in several places on the Great and Little Orme’s Head frag- 
ments of: buff chert lying on the surface. One of the men engaged 
at the Nant-y-Gamer sand-pits told me also that similar ‘ white 
stuff’ was dug a few miles inland near Holywell and Bagillt, and 
