Geological Society. 571 
of the boulders, and their diminution in size and quantity from north 
to south. It might also be contended that we have no right to infer 
the existence of a colder climate in our latitudes in those days ; but this 
objection does not appear unanswerable, since it might be replied, 
that if at the period of the northern drift England, Ireland, and the 
continent of Europe were united by a lofty chain of mountains, there 
might have been a temperature sufficient to have formed annually 
large bodies of ice on the shores of Cumberland. Passing however 
from this difficult question of the method of transport, Mr. Murchison 
states that the greatest of the anomalies hitherto presented by these 
boulders is obviated, when we dispel from our minds the idea of their 
having been carried over preexisting lands. Having once ascertained 
that large distributions of them took place under the sea, the different 
heights at which we now find them may, he supposes, be satisfactorily 
accounted for, by movements of elevation and depression acting upon 
the bed of the sea with unequal measures of intensity, raising up shells, 
gravel, and boulders which were accumulated at the same period, to the 
respective levels which they now occupy, doubtless producing many of 
the cracks and fissures with which the solid strata are replete, and 
leaving denuded valleys between the points so elevated. 
Feb. 24.*—A paper was first read, entitled “‘ Observations on a 
Patch of red and variegated Marls, containing Fossil Shells, at Colly- 
hurst, near Manchester,” by J. Leigh, Esq., and E. W. Binney, Esq., 
and communicated by Roderick Impey Murchison, Esq., F.G.S. 
Manchester stands on a slightly elevated platform of upper new 
red sandstone ; but the country to the north-west, north, and east of 
the town rises to a considerable height, and is traversed by the valleys 
of the Irwell, the Irk, and the Medlock, which furnish the only natural 
sections of, the district. The formations exhibited in these valleys, and 
supposed to extend under Manchester, are, first and lowest, the car- 
boniferous group; secondly, the lower red sandstone and marls ; 
thirdly, the magnesian limestone ; fourthly, the lower red marl; 
fifthly, the upper red sandstone; sixthly, the upper red marl; and 
seventhly, the superficial detritus. 
The principal object of the authors being to describe the upper red 
marl, they notice briefly the characters of the other deposits. 
The accumulations of superficial detritus are sometimes thirty feet 
thick, capping nearly all the high ground, and extending over the val- 
leys. In the lower part they consist of water-worn fragments of gra- 
nite, greenstone, porphyry, claystone, mountain limestone, and coal 
measures, imbedded in sand ; and in the upper, of stiff blue clay, 
containing partially rounded fragments of the same rocks but of 
greater size. Portions of the lower red sandstone and marl are some- 
times found, but none of the magnesian limestone. Blocks of granite, 
weighing two or three tons, occuron the summit of some of the hills 
which surround the Irwell and the Irk, 
The lower red sandstone, the magnesian limestone, and lower red 
marl are exposed at Worsley Mills and at Stockport, dipping conform- 
* The Anniversary Proceedings of Feb. 19, will be found at p. 310, in 
our Number for April. 
