T. IT. Struthers — Tertiary and Post- Tertiary. 



397 



at various times. Thus the Chalk of the Hog's Back and Culver 

 Cliffs was placed at its present angle by differential elevation during 

 post-Bagshot times. The occurrence of Crag at Lenham seems to 

 show that that portion of the country was submerged when the west 

 was dry land. According to Prof. Prestwich, the old beach which 

 is 8 to 12 feet above the sea at Brighton rises to 100 feet near 

 Arundel, to 130 feet near Chichester, and to 140 feet at Bourne 

 Common, and then falls to 125 feet above the sea at Portsdown Hill 

 (Q.J.G.S. vol. xxviii. p. 38, Topley, Weald, p. 286) ; and if this is so, 

 we have not only evidence of differential elevation, but of elevation 

 in a curve instead of a straight line. 



My conclusions are : — 



1. — That during the deposition of the Wealden and Neocomian 

 beds in the south-east of England, the area was one of depi'ession, 

 that the rate of depression of the centre was in excess of that of the 

 surrounding area, thus causing the thickening of the beds towards 

 the centre. 



2. — That upon the area becoming one of elevation, the elevation 

 was most rapid in the centre. 



3 — That a large portion of the beds were removed by marine 

 denudation as they rose out of the sea, a large sandy plain thus being 

 formed ; and that the plain of marine denudation spoken of by authors 

 was not due to the advance of the sea over land. 



Note. — Since this was written Prof. Prestwich's papers on the 

 Westleton Beds have been published. He appears to attribute more 

 of the denudation of the Wealden area to subaerial agencies than 

 former authors. — H. W. M. 



IV. — Tertiary and Post-tertiary Stratigraphy. 



By Thos. E. Struthers. 



Hon. Assoc, and late Vice-President, Geological Society of Glasgow. 



AS a basis for the following observations on the classification of 

 Tertiary and Post-tertiary strata, we submit a comparative view 

 of the nomenclature adopted by various authors. 



Note. — The segregation of the Oligocene from the Eocene had not been effected when 

 Lyell and Jukes wrote. 



From the above table it will be noticed that Lyell and Hull 

 assign the Glacial period — called by the former "Newer Pliocene," 

 and by the latter " Post-pliocene " — to Tertiary or pre-human 

 time ; and the first appearance of Man in Europe to the period of 



