1865.] WATSON PARALLEL EOADS OF GLEN EOT. 9 



about the Mendip, Quantock, and Exmoor ranges ; but there is no 

 evidence whatever that the great characteristic part of that fauna was 

 in occupation of the area at more than one period. It became extinct, 

 even over the area of the South of England, which was not sub- 

 merged ; indeed the extensive subaerial glaciation which that area 

 has undergone from Cornwall to Kent and Sussex, is inconsistent 

 with the existence of such a fauna. 



Lastly, with reference to the age assigned to these later changes, 

 subsequent to that of extreme cold, a relative date is arrived at for 

 many of the so-called " Eaised Beaches " occurring on our western 

 coasts. The example nearest to Porlock in the West is that between 

 Braunton and Baggy Point, long since so well described by Sir R. 

 Murchison and Professor Sedgwick. At this place there is the evi- 

 dence of the more recent changes at low levels, the older sea- 

 bed, at an elevation of 60 feet for its higher portions, being covered 

 up by an enormous accumulation of angular debris-bed *. 



I have already called attention to the great thicknesses and other 

 characters of the angular debris overlying old sea-bed (Quart. Journ. 

 Geol. Soc. vol. vii. p. 118), and would also refer to the observations 

 of Sir H. De la Beche (Eeport on Cornwall, &c., chap. 13). 



In a modified sense these sea-beds or raised beaches are pre- 

 glacial, or older than the period of deep surface disintegration. But 

 just as the amount of northern depression increased from South 

 Northwards, so the progress of that depression was in the contrary 

 direction, or from North to South ; the line of the Bristol Channel 

 was nearly the limit of this submergence, and was the last reached. 



The interval of time which separates these more recent changes 

 of relative level from that of the great depression of the Northern 

 Hemisphere, is possibly very great, not so their distance from the 

 present. The distinctive features of the newer deposits are, that they 

 belong to the time of our existing assemblage of animals and plants, 

 that they indicate changes of small vertical amount, and are remark- 

 ably uniform. 



2. On the Maeine Oeigin of the Paeallel Eoads of Glen Roy. 

 By the Rev. R. Boog Watson, P.R.S.E., E.G.S. 



(Abstract.) 



The Parallel Roads of Glen Roy have been described by several 

 observers, who have also offered explanations of the manner of their 

 formation. In the author's opinion, Mr. Robert Chambers has 

 solved this problem in his ' Ancient Sea Margins,' and in this 

 paper he supported the view there advocated, and offered some 

 objections to the theory of an ice -dam, originally put forward by 

 Prof. Agassiz, and recently illustrated by Mr. Jamiesonf. 



After noticing the strong points of the ice-dam theory, Mr. 

 Watson remarks that, though Prof. Agassiz and Mr. Jamieson agree 



* Eed a of Section. Geol. Trans. 2nd ser. vol. v. p. 279. 

 t Quart. Journ. Geol. Soc. vol. xix. p. 235. 



