AN5TVEBSARY ADDRESS OF TRE PRESIDENT. ll 



in the British Isles ; we shall have the following scale of time against 

 the three great divisions of the stratified rocks* : — 



In which the earliest group 



100 



8 





feet, 

 2240 



occupies 79, the middle 



IK 





13190 



group 18, the latest only 









3 parte. 











70. 





0T154 





72084 







From such a diagram immediately arises the important inference, 

 that in the earlier periods of the world's history the changes of life 

 in the sea were accomplished at a rate much less rapid than that 

 which prevailed in later times, which agrees with the acknowledged 

 very wide distribution of palaeozoic forms in geographical Bpacoi 

 Admitting the changes of life on the whole 1" be equal from the 

 Palaeozoic to the Mesozoie, and from these to the Caenozoic periods, 

 we find the rate of progressive change 7 ' cr for Palaeozoic, J* far M>- 

 sozoic, and A- for Caenozoic time, — a conclusion Of great importance. 

 and probably indicative of the greater influence and superiority in 

 early times of a slowly changing physical condition of the whole 

 globe over the partial and irregularly varying local conditions. Which 

 were continually augmenting and are still augmenting in influence 

 with the lapse of time* Such a superior influence has been ascribed 

 to greater uniformity of terrestrial temperature than is now expe- 

 rienced, 



§ Conversion of Geological into Historical 77,,,,-. 

 It is possible by some hypothesis of the annual waste of the .sur- 

 face of Land, or the annual deposition of sediment) as now observed 



in the sea. at the mouths of rivers or in lakes, to transform the unit 



oi geological time above suggested into an equivalent term of 3 



but the numbers which result for the age of any given rook, Like 



those which represent the circumference of B circle in terms of its 



diameter, are osuallj bo Large as to elude the -rasp ,,c memory ot 

 imagination. As an example. Lei the Wealden group of B 

 taken, with its thousand feet of deposits of sand, clay. &c formed 

 by the action of an ancient river flowing through forests of a tropical 

 aspect, and nourishing reptiles of a oorresponding character. I I 

 the ii\er be Mummed as equal to the Ganges in its power of trans- 

 porting sediment and in its extent of drainage, The sedimenl 

 by smh a riv.r at its mouth might amount to a thiol | inch 



* The tbiefalBSMB ate token froft Professor Ramsay's coimiiimicatioii 1 

 Darwin. 



