File:The Quarterly journal of the Geological Society of London (13205760615).jpg

182 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. .Jan. 6,
terly Journal of the same year,) certain deposits were described
under the term Diluvium^ consisting of " yellow sandy loam with
patches of gravel, and rounded masses, chiefly of insular rock, de-
veloped on the mountain sides, and filling up the valleys in the in-
terior of the island." This formation he ascribed to a transporting
diluvial action, principally from the north-east, during the prevalence
of an arctic climate. The difficulty presenting itself was, that whilst
blocks of the South Barrule granite are found driven over the top of
South Barrule 600 feet above the granitic boss, and at a height of
1545 feet above the present level of the sea, and are plentiful on the
south-western side, blocks of the same granite are scattered also over
the southern area of the island, and are found at points even south-
eastward of the granitic boss.
The author is now inclined to place a larger portion of these de-
posits, than he had previously done, under the head of the Boulder
Clay formation, which he supposes to havebeenaggregatedin an arctic
climate belotv the then ordinary sea-level, and by ordinary currents
without any necessarily violent diluvial action, though he would not
by any means exclude such an action at intervals during the forma-
tion. He now presumes that an elevation of the sea-bottom to the ex-
tent of at least 400 feet has taken place in this neighbourhood since
the period of the boulder deposit, and he is inclined to think that the
curved line on the southern side of South Barrule, indicating the ex-
tent of the tertiary formations (coloured yellow in his general Map
of the Isle of Man), points out very nearly the ancient sea-shore of
that period. These conclusions are based on an examination of the
conditions which seem requisite in order to account for the occur-
rence of the insulated mass of the boulder formation in the before-
mentioned locality in the Calf of Man.
The mass itself (which is about thirteen feet thick and fifty feet
across in each direction) consists, as just stated, of boulders, gravel
and sand. The sand is chiefly at the base of the formation, and in
it occur a few pebbles and laminae of fine gravel ; as we ascend, the
size of the fragments of rock increases; we have a bed of fine, then
of coarse gravel, and the uppermost portion consists generally of
large rounded pebbles with good-sized boulders which are scratched
and grooved. Most if not all the rocks are foreign. There are not
any which the author can certainly claim as belonging to this locality.
Section (4.)
Ill
III
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