1873.] JTJDD THE SECOND AKY ROCKS OP SCOTLAND. 147 



beds in the immediate neighbourhood, through being let down by 

 faults, is a phenomenon familiar to every geologist, and, indeed, is 

 illustrated by wonderful examples cited in the present memoir. That 

 landslips acting during the Glacial epoch might have produced a 

 similar result on a small scale is clear ; and, indeed, examples of the 

 kind have presented themselves to me during my survey of districts 

 thickly covered with drift in the Midland counties of England*. I 

 have already shown reasons for believing that the Secondary strata 

 were largely developed in the Elgin district. 



On the other hand, the principal objection which has been raised 

 to the hypothesis that the Linksfield mass is a boulder f, namely 

 that of its great size, has been effectually disposed of by the discovery of 

 undoubted transported masses of equal, and even greater dimensions, 

 imbedded in the Boulder-clay of other districts J. 



It is not my purpose to attempt to decide between these two 

 hypotheses, both of which appear to harmonize equally well with 

 all the phenomena of the case — the glacially striated and polished 

 rock at the bottom of the section, the overlying and underlying 

 Boulder-clay, containing detached fragments of the same beds, and 

 sometimes filling fissures in the principal mass, and the contorted, 

 cracked, and sometimes dislocated appearances presented by the 

 latter. The two hypotheses have some points in common ; for it is 

 evident that in order to account for the transportation of such enor- 

 mous masses by means of ice rafts, we must suppose that they have 

 been deposited on the surface of the ice-foot by means of landslips. 

 Perhaps it will be more logical in all such cases to avoid calling in 

 the agency of these vast ice-floats except in the cases (of which there 

 are many) in which it can be clearly shown not only that the 

 rocks composing the masses are absent in the neighbourhood now, 

 but that it is impossible that they could have existed in the vicinity 

 as escarpments during the Glacial period. 



The section at Linksfield is now unfortunately closed, the quarry- 

 ing of the limestone below the shales and Boulder-clay having been 

 abandoned. Admirably detailed descriptions of the succession of 

 the beds, however, have been published by Malcolmson§, Duff||, 

 Brickenden^f, and Moore**. 



Although the Linksfield beds are highly fossiliferous, there is con- 

 siderable difficulty in fixing their exact age. The fallacy of the 

 arguments derived from the mineral characters and the succession 

 of the beds, on the strength of which they have been successively 



* These and many examples of transported masses of enormous dimensions will 

 be described in a forthcoming memoir of the Geological Survey. 



f Symonds, Edin. New Phil. Journ. New Ser. vol. xii (1860) p. 100. 



| See Morris, Quart. Journ. Geol. Soc. vol. ix. (1853) p. 317; Ramsay, ibid, 

 xxvii. (1871) p. 252 ; also Fisher, Geological Magazine, vol. v. (1868) p. 407 ; and 

 Bonney, ibid. vol. ix. (1872) p. 403. 



§ Proc. Geol. Soc. vol. ii. p. 667 ; and Edin. New Phil. Journ. New Ser. 

 vol. ix. (1859) p. 48. 



|| Sketch of the Geology of Moray, p. 15, plate iii. 



% Quart. Journ. Geol. Soc. vol. vii. (1851) p. 291. 



** Ibid. vol. xvi. (I860) p. 440. 



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