502 J. Stnrlde Gardner — Relative Ages of 



newer than any except the youngest Chalk in England. These con- 

 clusions would be fully borne out by physical and stratigraphical 

 evidence, if there were time to examine it liere. The Cretaceous 

 series in Bohemia, Gosau, and Poland would, I believe, go far 

 towards connecting the Secondary and Tertiary periods. 



Eeturning, however, to our typical area, England, we are con- 

 fronted with one of the most considerable gaps in the whole of the 

 geological record. So complete does the break appear that the 

 earlier geologists made it their line of demarcation between the 

 Secondary and the Tertiary periods. 



While Chalk or Clobigerina ooze was being deposited in ever- 

 widening circles, the central area must have been becoming still 

 more abyssal, and the deposition of matter over it continuous, 

 though perhaps in lessening quantities. It is scarcely possible that 

 this sea-bottom could have been at once uplifted into dry land, and 

 it is more reasonable to suppose that it shallowed as gradually, and 

 the sea retired as slowly, as it had advanced. Thus, if our series 

 were complete, we ought to possess a passage back through green- 

 sands to littoral mud or sand. Instead of this, the geological record 

 fails us, and our series terminates abruptly in its central area with 

 deep-sea deposits, the newest of which is old relatively to some called 

 Cretaceous in other countries. The Faxo, and to some extent the 

 Maestricht limestones, mark the retreat of the Cretaceous sea, and 

 a period when the waters had shallowed enough to permit the 

 growth of Coral ; but in England the complete change that had 

 taken place in organic life of almost every kind shows that the 

 missing strata might far exceed in importance even the entire 

 Cretaceous and Eocene formations that remain to us. The denuda- 

 tion of the Chalk has been on a stupendous scale, and had doubtless 

 proceeded for ages before the deposition of the Eocene commenced, 

 since even their lowest beds consist of extensive tracts of flint 

 ground into sand and pebbles. It has continued ceaselessly ever 

 since, to how great an extent we learn but imperfectly, by the 

 enormous beds of gravel and sand which compose, to a large extent, 

 the Tertiary gravels and shingle, and that of our present littoral. 

 Our Eocenes are from base to summit the accumulations of a river 

 which drained a continent, in part upheaved from the bed of the 

 Cretaceous ocean, and which must have been deeply covered with 

 Cretaceous sediment. Continuously carried away in solution by 

 rain water and springs ; undermined and planed down by the sea 

 to its own level, no matter how towering its cliffs, and with the 

 planing action assisted by every oscillation of level throughout the 

 whole Tertiary period, we need feel no surprise that so mere a 

 fragment of the Chalk foi'mation remains. 



If much that I have said appears so simple and obvious that it 

 might well have been treated as a matter of course, its consideration 

 was absolutely necessary to prepare us for that of my actual subject. 

 It was as essential to master these rudimentary facts in the present 

 inquiry, as it would be to take account of the characters of an 

 unknown alphabet, before trying to decipher the meaning of an 

 inscription formed from them. 



