GEOLOGY. 
171 
imbedded in the sandy soil of the beach, but many are insulated and exposed. The 
empty cavities in some of them are as large as a man’s list. The sand of the beach 
partakes of the black and volcanic nature of these blocks, and so continues to Cape 
Espenberg, where the large stones are no longer seen. These large and numerous 
blocks, collected chiefly on the jutting points, must have been conveyed there by some 
grand convulsion of nature, from a very considerable distance. No volcanic formation 
is to be seen in the vicinity. — C. 
CAPE THOMSON. 
Remarks on the Stratification of Cape Thomson, in lat. 67° O’ N., long. 165° 45' TV. 
A section of this part of the north-west coast of America is given in plate II. 
Geology, from a map by Lieutenant Belcher. The summit of the northernmost cape (A) 
is composed of carboniferous lime-stone, abounding with organic remains similar to (hose 
of the lime-stone of Derbyshire. It is also traversed by veins of chert of a blackish 
cast, varying in thickness from six inches to two feet. It here dips at an angle of 10° to 
the westward, and is succeeded, about half way down the cliff, by blue and black argil- 
laceous sbale, with which it alternates in strata of six or eight feet in thickness ; and 
at about two-thirds down to the base, shale alone occupies the cliff, and becomes 
abundant in organic remains ; it is occasionally interstratified by lime-stone, and much 
contorted. This contortion is so great as to form two regular arches ; the beds at the 
lowest part are so much bent as to be doubled back on themselves. At this point of 
greatest contortion, they are cut off by a gap, where a stream (which must be very 
powerful during the thaws in the earlier part of the season) had destroyed the con- 
tinuity, but still left sufficient to trace the connexion with the east side of the stream, 
where the shale ceases to be contorted. Here, as we ascend the cliff B, we find the 
lime-stone and chert resumed in rectilinear strata, dipping at an angle of 150° to the 
westward. At the east base of B, beneath the lime-stone, there is a recurrence of con- 
torted beds of shale, similar to those at the base of A, but more abundant iu veins of 
calcareous spar, pyrites, balls of septaria, and compact lime-stone containing tubiporite, 
encrinite, &c. 
At the end of the bay, the lime-stone again commenced, of nearly the same character 
as A ; the chert, however, assuming a greyish cast, end containing organic remains in 
profusion ; and under nearly the same circumstances as at A, the slaty shale underlaid 
the lime-stone, but was covered in some places by a saline efflorescence (of sulphate of 
lime), proceeding apparently from the decomposition of iron pyrites. Many of the 
pieces contained crystals of carbonate of lime and selenite. Some chert which had 
fallen from the centre of the cliff, I found loaded with layers of shells (chiefly bivalves). 
The chert appears to be the same as that from which the natives make their arrow- 
heads ; and with the assistance of a small piece of bone, slices of it are easily reduced 
to form: the manner in which they work it shows their acquaintance with the flat 
conchoidal fracture, of which they take advantage. The height of the cliff A, which is 
the highest of the two, is about 400 feet. 
