Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/844

732 732 D. MACKINTOSH ON SOME NEW SECTIONS Floating coast-ice holding the stones firmly fixed in its base, and grinding them against projecting sandstone rock-surfaces in a shallow sea, would seem to offer the most satisfactory explanation*. In the upper clay the stones are similarly grooved, with this ex- ception, that irregular scratches and cross sets of grooves are not nearly so frequent. Signs of Boulders having been dropped. — South of Dawpool Cot- tage 1 once saw two instances (in the lower clay) in which boulders had evidently fallen from a certain height, so as to press the clay violently, develop its latent lamination (?), and cause the laminae to rise up at the sides (fig. 2). Pig. 2. — Fallen boulder, Dawpool. Sections on the West Shore of the Estuary of the Mersey. — A long section, exhibiting phenomena which are a repetition of those seen at Dawpool, extends for some distance on each side of Egremont Ferry. Mr. De Ranee, F.G.S. (who has done much to establish the threefold division of the drifts in Lancashire, and who has offered many excellent suggestions concerning the origin of these drifts), notices a part of this section in Quart. Journ. Geol. Soc. vol. xxvi. p. 644. I have lately carefully examined it under favourable cir- cumstances, as many fresh faces (April 1877) have been exposed in excavations for bricks, &c. An extended survey shows that the lower clay here is not invariably separated from the upper clay by stoneless sand and loam ; while the latter, so far as I could see, likewise occur in patches and beds in the lower clay. But the line of junction between the two clays, where clay-slips have left fresh faces, can easily be detected. The upper clay, with its frequently recurring grey-faced and vertical fractures, is seldom more than 12 feet thick. In a brick-pit east of Egremont Ferry it has been excavated down to a level floor of sand. The existence of two clays is well known among brickmakers. While the upper is found to be the best brick-clay, the lower is too " strong " for making good bricks. There is likewise a difference in the number of contained stones, and in the colour of the two clays ; but it ought not to be forgotten that the colour of all clays changes with the amount of moisture they contain. During recent excavations to obtain a foundation for a sea-wall, the lower clay (of which there is a great ciated on the hill-sides or in the valleys of the Lake-district.
 * During repeated observations I have seen few or no stones similarly gla-