BRITISH ASSOCIATION MEETING. 
461 
tingiiislied from that beneath, while, by the same means, the middle elav is with 
equal ease separated from those clays above and below it. The rock dips 
down to the south, and at a distance of three miles the middle clay is replaced 
by sand. 
rive miles north of Elsworth the St. Ives rock comes to the surface, and 
dips to the east. It is a hundred and thirty feel beneath the Elsworth rock, 
and very similar to it in mineral character. Its thickness is three feet, often 
divided into two beds by a parting clay. It is brought up by an anticlinal, so 
that on high ground four miles north the Elsworth rock is again met with. 
Six miles west of Elsworth is found the St. Neotts rock, which is deep down 
beneath the St. Ives rock, though not so low as the zone of the Kelloway 
rock. 
But for the breaks by these rocks, the lowest beds of Oxford clay would 
fadiiate up, without any perceptible change in life, into the highest beds of the 
immeridge clay, the coral-rag being absent as such, but represented by a clay. 
This clay contains a mixture of the fossils of the clays above and below, and 
is met with above the Elsworth rock at Elsworth and Bluntishara. From the 
exhibition at the latter place it is named the " Blunt'shara clay." The clay 
beneath the Elsworth rock is the Oxford clay, so that the Elsworth rock is 
intermediate in position between that subdivision of the great clay formation 
and the coral-rag. The fossils unmistakeably show it to belong to the clay 
rather than the limestone formation, and hence it will be regarded as the 
highest zone of the Oxford clay, while the St. Ives, St. Neotts, and Kelloway 
rocks will serve to mark the several zones into which the formation is naturally 
divided by its fossils. 
Thin rocks have also been met with in the Bluntisham clay in positions 
which render it probable that they indicate divisions corresponding to coral-rag 
and calcareous grit. 
ON THE PLEISTOCINE DEPOSITS OF NORTH AMERICA. 
By Dr. Hector. 
The author stated, that his recent researches in that country afforded strong 
grounds for supporting the view, that the diffusion of the erratic drift must have 
resulted from the submergence of the north-east part of the Continent beneath 
an arctic sea to a depth of nearly 3000 feet, and that the surface of the country 
has received much of its present form by denudation during its re-emergence, 
at first along sea-coast lines, and latterly along the shore lines of inland lakes, 
vhich still exist, but of much smaller size than formerly. By the steppes which 
have thus been found these deposits may be divided as follows : — 
Bordering the lower part of the valley of the St. Lawrence and extending 
southwards through the valley of Lake Champlain, a marine deposit of boulder 
clay has been described with mollusca, more arctic in their character than those 
existing in the neighbouring seas at the present day. This deposit has not 
been observed at a greater altitude than 600 feet,* and in its nature it would 
seem to resemble those deposits that must be forming at present in Hudson Bay 
and in the Arctic inlets and sounds, where the shore ice, kept in motion by the 
winds and tides, acts like a pug-mill in reducing the previously deposited drift 
to the condition of tough clay. 
On the shores of Puget Sound and the Gulf of Georgia, in latitude 49° N., 
on the west side of the Continent, there are drift clays with boulders and 
scratched rock surfaces, which, like those clays in the St. Lawrence Basin, do 
♦ Lyell, Rogers, Desor, &c. 
