MR DAVID MILNE HOME ON THE BOULDER-CLAY OF EUROPE. 675 



by a sandy boulder-clay, which, having been in motion, has squeezed or lent the 

 ends of the sandstone and shale towards the S.E." Two other localities are 

 mentioned by this observer, where the outcropping strata of shale had been in 

 like manner broken off and carried towards the S.E., by some agent pressing 

 down upon them. 



Dr Howden, in describing the superficial deposits of Forfarshire ("Edin. Geol. 

 Soc." vol. i. p. 139), says that " in the Brechin Quarry, and in other localities, 

 where the strata are nearly horizontal, especially if they consist of thin laminae, 

 the rock has been broken up into shivers, large detached masses being embedded 

 in the {boulder) clay" Dr Howden suggests no explanation, but it is evident 

 that here also some agent must have ploughed up the strata, and disturbed the 

 covering of clay. 



I might refer also to the curious foldings observed in beds of clay, and even 

 of sand, which both Sir Charles Lyell and Mr Geikie admit cannot be ex- 

 plained in any other way, than by supposing that icebergs or heavy masses of 

 floating ice had pushed them out of their original position.* 



But the most remarkable case, where boulder-clay is shown to have been 

 pushed and pressed forward en masse, was described some years ago by two 

 most competent observers, Captain Brickenden and Mr Martins of Elgin, ob- 

 servers who wrote independent reports, the former in the " Proceedings of the 

 Geological Society of London," f the other in the " Edinburgh Philosophical 

 Journal"! some years afterwards. Being much impressed with the importance 

 of the facts related by both observers, and wishing to obtain further information, 

 I wrote to the only one whose address I could discover, Mr Martins, and received 

 from him a letter, in which the following passages occur : — 



"The Linksfield strata consist of a series of bands of limestone, shales, and 

 blue clay. These have obtained the name of Wealden, from the fossils in them. 

 Under these bands there lies a great deposit of limestone, called Cornstone. In 

 some places, the Wealden bands are separated from the Cornstone by intercalated 

 boulder-clay, having all the characteristics of boulder-clay met with throughout 

 the country. It has the same tenacity, and the same want of stratification, and 

 contains the usual travelled pebbles and blocks. The only difference observable 

 is, that the clay when intercalated has a purplish tinge, evidently acquired by 

 contact with the blue clay of the Wealden. It also contains fragments of the 

 limestone from the band lying immediately above it. In some instances, large 



* Lyell, "Antiquity of Man," p. 138. Mr Geikie ("Glacial Drift," p. 119), after alluding to cases 

 where " beds of clay were fairly bent back upon each other," says, " such contortion must lie due to 

 powerful pressure. It may have been produced oy masses of ice standing here, and pushed onward, 

 partly by their own impetus, partly by the action of winds or currents. The compression to which 

 such a weight of ice would give rise, would probably be quite sufficient to corrugate beds of clay and 

 sand." 



•j- Proceed, of Geol. Society for 1851, vol. vii. p. 289. 



J E. Ph. J. for 1856, vol. iv. p. 222. 



VOL. XXV. PART II. 8 N 



