A. Bell — Succession of the Later Tertiaries in Qt. Britain. 67 



VI. — The Succession of the Later Tertiaries in Great Britain. 

 By Alfred Bell. 



THOSE interested in the geology of the Upper Tertiaries must 

 have noticed the divergence in the views entertained by different 

 writers as to the succession of the various strata of which they are 

 composed. Sundry causes may be assigned for this, such as the 

 disposition in some quarters to regard the " lapse of time occupied in 

 the accumulation of even our later Tertiary deposits " " as repre- 

 senting but a very brief chapter in geological history," * or the 

 massing of the several groups of strata in bulk, or putting aside as 

 of little value the organic evidence they contain, which, even where 

 this is appealed to, is too narrowly treated, as where one author — 

 a specialist in his own branch — asks, ''Could the more modern 

 Tertiaries be classed by their Invertebrata ? " 



Not alone perhaps ; but if all kinds of life are studied in corre- 

 spondence with their surroundings, a natural sequence can be traced 

 throughout their entire history. 



Astronomical speculations as to the time when the Glacial epoch 

 commenced or terminated, and the attempts thereby to determine 

 the existence of Man upon the Earth, may be set aside as of little 

 value at present; as Mr. Prestwich happily puts it, "the difficulties 

 arising from astronomical theories are that they differ so much among 

 themselves." 8 



A fair inference as to the time required may be drawn from the 

 fossils. My lists give of the Eocene about 2500, and of the later 

 Tertiaries above 3000 species, hardly any being in common. 



In the following notes I have assumed that the constituents of the 

 different deposits and their fossils are pretty well known to geologists, 

 and I have therefore not attempted to locate every known bed, but to 

 indicate the lines on which their classification is possible. A com- 

 parison betwixt that which I have here attempted and that adopted 

 by Mr. J. Geikie will, I may say at once, indicate how widely 

 divergent our respective views are. I take his as a standard of com- 

 parison as being the most extensive one brought forward hitherto. 



I am probably biassed, but I cannot see any evidence in favour 

 either of the numerous mutations of the surface, or alternate pro- 

 cession of the Northern and Southern Mammalia suggested in the 

 " Great Ice Age," or that Britain was ever otherwise than Continental 

 from the close of the Middle Bed Crag age to that of the minor 

 glaciation, about which time I consider it ceased to be so. 



It may be laid down as a general rule that the fauna and flora 

 march with the climate, i.e. cold with cold or the contrary, and that 

 if by any possibility the temperature of any period can be ascertained, 

 a corresponding organic life existed, circumstances being favourable 

 thereto. 



Of the preglacial deposits the admirable memoirs by Messrs. 

 Clement Beid and E. T. Newton leave little to be said. I may, 

 however, remark that the evidence of the Forest Bed being overlapped 



1 Dr. H. Woodward, On Mhytina gigas. 



2 Quart. Journ. Geol. Soc. vol. xxvii. p. 233. 



