Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/539

1869*] MACKINTOSH—LANCASHIRE AND CUMBERLAND DRIFTS. 415 have come from a less distance than Eskdale, would seem to favour the idea of floating ice; for while it is generally admitted that the bulk of land-glacial drift must be local, it is very improbable that a flow of land-ice from Eskdale, on reaching what is now the bed of the Irish Sea, should have turned round in the direction of Black-pool; and this improbability will still further appear when we take into consideration the fact that the primary striation of Northwest Lancashire is from north to south, or from north-north-east to south-south-west (see sequel).

3. Drifts between Lancaster and Carnforth.

Between Blackpool, Preston, and Lancaster the country is more or less covered with drift, which I had little opportunity of examining; and between the valley of the Lune and Carnforth my opportunities of observation were more limited than in the three other districts noticed in this paper. On walking from Lancaster to Carnforth one cannot fail to be struck with the enormous mass of drift which almost everywhere conceals the solid crust of the earth. Its thickness in many places cannot be less than 200 or perhaps 300 feet. Its surface is very undulating, in some places consisting of knolls like a flattened form of esker, in others presenting the appearance of parallel drumlins*, though on minute inspection it is seen that the latter are not sufficiently parallel or regular to be correlated with the drumlins of Ireland. I was unable to see any exposure of drift in which the line of contact between two distinct deposits could be clearly made out. At Hest Bank I fancied that the sea-cliff showed an indistinct line of demarcation between a hard Lower and a comparatively yielding Upper Boulder-clay, but could not make sure of the existence of more than one formation, and that apparently Lower Boulder-clay.

The two fine sections at Hest Bank consist of sea-cliifs cutting across drift-knolls. The one furthest from the railway station is about 50 feet in height. The clay is full of stones, of sizes varying from small pebbles up to very large boulders of limestone. They are much striated, and often rounded only on one side. Between here and Morecambe, and along the beach at Morecambe, large stones are generally found in groups, which might merely indicate the places where the Boulder-clay came to the surface, were it not that where this formation runs continuously for great distances along the coast the large boulders occur, with few exceptions, in groups—a circumstance which, if well established, would indicate their having been dropped by floating ice rather than left by land-ice†.

On the hill near Lancaster, called Lancaster Moor, a hard reddish sandy clay, very much resembling lower Boulder-clay in its structure, may be seen resting on a surface of millstone grit which has been glaciated either towards or from the valley of the Lune, in my


 * The Rev. M. H. Close (see Journ. Roy. GeoL Soc. Ireland, vol. i. part 3) believes that the parallel ridges called drumlins were accumulated under land-ice.

† In Staffordshire, Shropshire, &c. the boulders of granite, porphyry, and other far-transported rocks are generally found in groups.