CHRONOLOGICAL ESTIMATES 69 



main as monuments of the strains that accompanied 

 the great earth movement. I conclude, therefore, 

 that the dispersion of the surface debris, the forma- 

 tion of the Ossiferous fissures, the accumulation of 

 the " Head, 11 and the local ablations of the rocks, 

 are the necessary results of the Submergence and 

 subsequent Re-elevation of the land. 



. 9. DATE OF THE SUBMERGENCE. 



We are here confronted with very contradictory 

 opinions. The doctrine of Uniformity leads to such 

 extreme demands on time that CrolTs hypothesis, 

 which in that respect is in harmony with those views, 

 has been very generally adopted. According to Croll's 

 last estimate, the Glacial Period commenced 240,000 

 years and ended with the Post-glacial 80,000 years 

 ago. The latter date was supposed to correspond with 

 the close of the Pleistocene and Palaeolithic period. 

 It followed on this assumption that a vast interval of 

 time must have intervened between that period and 

 the Neolithic times. Were that the case, there ought 

 to be some geological evidence either in the form of 

 sedimentary deposits, or of work done in the ex- 

 cavation of valleys ; I fail to find either. So far from 

 there having been a vast interval of time between 

 the Palaeolithic and Neolithic periods, the strati- 

 graphical evidence shows that they follow quickly in 

 immediate succession. The deposits of the two 

 periods are in fact separated merely by a few feet 

 (and that only in places) of Rubble-drift from one 



