146 PEOCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 8, 



the beds at Linksfield to those of the Bhaetic formation in the south- 

 west of England, and he showed that there exists some palseontolo- 

 gical evidence in favour of identifying the two series. In this view 

 he was confirmed by Professor Rupert Jones*. 



The remarkable position of the mass of Secondary strata at 

 Linksfield has given rise to a number of hypotheses to account for 

 it. The chief of these are as follows : — 



(1) That the stratified clays and limestones once rested imme- 

 diately upon the Triassic limestone, and that the foot of a glacier or 

 iceberg forced the two sets of strata asunder, carrying with it a mass 

 of glacial detritus and scoring and polishing the hard surface of the 

 lower rock. This hypothesis appears to have been first suggested 

 by Mr. A. Eobertson, of Inverugie, and Captain Brickenden f, and to 

 have received the sanction of Professor Agassiz. 



(2) The hypothesis suggested by Sir Charles Lyell at the Aber- 

 deen Meeting of the British Association (1859) is as follows : — 

 " That a range of cliffs, of Triassic and Lower Liassic beds, rose 

 above the Yale of Elgin during the glacial epoch, when ice rafts 

 and drifting bergs, with all the phenomena of an Arctic sea, swept 

 down that vale, then a frith, and that the siliceous cornstone was 

 then the actual sea-bed. The icebergs and drifting masses under- 

 mined the soft marls of the Upper Trias and Lias, and in time pro- 

 duced a landslip. The whole side of a sea-cliff slipped down from 

 its position, on to a beach of Boulder-clay, without any boule- 

 versement of the strata " $. 



(3) The view first put forward by Dr. Gordon § and other local 

 observers, and since advocated by Professors Geikie and Bamsay||, 

 is, that the mass of Linksfield and similar masses in the neighbourhood 

 are really great transported blocks, which have been carried by ice 

 across the sea in which the Boulder-clay was formed, and quietly 

 deposited at the bottom by the stranding and gradual melting of 

 the ice rafts. 



The results of the more careful and exact studies of the modes of 

 ice-action made during recent years have been such as, I believe, to 

 lend but little support to the first of these hypotheses, while on the 

 contrary they have, by furnishing undoubted examples of analogous 

 action and by showing the futility of supposed objections, removed 

 many of the difficulties which prevented the acceptance of either of 

 the two other hypotheses. 



The preservation of a mass of strata, higher in the series than the 



* Monograph of the Fossil Estherise (Palseontographical Society, 1862), pp. 74- 

 77. 



t Quart. Journ. Geol. Soc. vol. vii. (1851) p. 291 See also A. Eobertson, in 

 Anderson's ' Guide to the Highlands,' 3rd ed. (1851) p. 344 : a similar view ap- 

 pears to have been binted at by Mr. Duff, ' Sketch of the Geology of Moray ' 

 (1842). 



J Symonds in Edin. New Phil. Journ. New Ser. vol. xii. (1860) p. 100, and 

 Quart. Journ. Geol. Soc. vol. xvi. (1860) p. 459. 



§ Edin. New Pbil. Journ. New Ser. vol. is. (1859) p. 52. Ibid. vol. iv. (1856) 

 p. 223. 



D Quart. Journ. Geol. Soc. vol. xxvii. (1871) p. 252. 



