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 



* During repeated observations I have seen few or no stones similarly gla- 

 ciated on the hill-sides or in the valleys of the Lake-district. 



