Geological Society. 341 
the sea. The same author also reported to us that he had disco- 
vered similar gravel with recent marine shells overlying a peat 
bog near Shrewsbury, in which were the remains of a submerged 
forest. Mr. Murchison, however, having examined this spot, has 
shown us that the supposed trees were stakes with sharpened puints. 
driven into the ground, forming a woodwork which supported an 
old road, and over these piles the shelly gravel or northern drift 
had been afterwards spread artificially. I understand that Mr. 
Trimmer is now fully aware of the mistake into which he had 
fallen. 
From the evidence afforded by the shells, as well as by the indica- 
tion of several newly discovered localities where they occur sixty 
miles from the nearest sea-coast, Mr. Murchison infers that the tracts 
covered by them must have formed the bed of the sea during the 
modern period, and as the granitic drift occupying the high grounds 
east of Bridgnorth rises to the height of 500 or 600 feet, and thence 
descends in a deltoid form into the Vale of Worcester, he conceives 
that the sea also extended over the valley of the Severn from Bridg- 
north to the Bristol Channel, so that there was then a strait sepa- 
rating Wales and Siluria on the one side from England on the other. 
The deposits observed by Mr. Strickland at Cropthorne and at 
other points in the valley of the Avon, an eastern tributary of the 
Severn, and which contain fluviatile and land shells, with the bones 
of extinct quadrupeds, must, according to Mr. Murchison, have 
been accumulated at the mouth of a river which flowed from the 
east, or from the Cotteswold Hills, into the ancient straits above 
alluded to, and into which the northern drift was prolonged. 
There are sections near Shrewsbury from which Mr. Murchison 
has been enabled to deduce the relative age of the two alluvial for- 
mations, the local or Welsh drift having in those places been found. 
covered by the clay and boulders of the northern drift. The latter 
is, therefore, evidently of newer origin. As to the mode in which the 
erratic blocks were transported, Mr. Murchison adverts to the 
possible agency of ice-floes, and to thedifficulty of imagining that cur- 
rents of water alone, whether of rivers or the ocean, could have ex- 
erted a force adequate to their removal to such great distances; many 
boulders of several tons in weight having been transported to more 
than 100 miles from the nearest possible source of their origin. 
He also infers from the position of the shells, gravel, and boulders, 
that they were not washed, as has sometimes been imagined, by 
one or more diluvial waves over preexisting lands, but were all de- 
posited during the same period in the bed of the sea, which bed 
was afterwards uplifted to unequal heights by movements of eleva- 
tion of unequal intensity—movements which, though so largely 
affecting the physical geography of our island, must have taken 
place within the modern era. 
Mr. Edward Spencer has communicated to us the result of his 
examination of the “diluvium” near Finchley, and the summits of 
the neighbouring hills of Highgate and Hampstead. The gravel 
there contains water-worn boulders of granite and porphyry, toge- 
