XCU PROCEEDINGS OE THE GEOLOGICAL SOCIETY. 



fondly trusting to, do not really exist in nature. I believe the time will 

 come, when, having brought before us a greater amount of sections 

 all over the world (if indeed it is not possible to do so already), we 

 shall find that there exists a gradual passage from the very oldest to 

 the newest strata ; that from the earliest fossiliferous rocks to the 

 most recent post-pliocene formations there has been one unbroken 

 sequence of deposits, modified only by local disturbances, showing 

 the gradual change of organic life according to the different conditions 

 of existence ; that in every case a certain number of species existing 

 in the beds below have been continued upwards, mingled with new 

 forms specially created to suit the new state of things ; and that this 

 progress has ever been going on in some part of the earth's surface, 

 undisturbed by other local changes and convulsions. We know that as 

 the conditions of life varied, new forms were called into existence, while 

 former ones were gradually disappearing ; but Ave shall, I think, be 

 more and more forced to give up that view which led us to subdivide 

 the countless myriads of ages of geologic time into epochs, forma- 

 tions, groups, and subdivisions, and to look upon the whole series as 

 one grand group modified in time by a slow and imperceptible pro- 

 gress, and affording breaks and interruptions of conformability of 

 strata only as local phsenomena. This difficulty, as I said before, is 

 gradually increasing, and to guard against it we require not only 

 caution with regard to ourselves, but toleration towards others who 

 are disposed to place the local limits of those formations, to the 

 nomenclature of which we must still adhere for the sake of con- 

 venience and description, otherwise than where we are inclined to 

 place them ourselves. 



Again, although it may sound to some like a geological heresy, 

 I would add one observation more, in the shape of a caution 

 against our allowing ourselves to be led to trust too implicitly 

 to mere paleeontological evidence. The errors which may proceed 

 from this cause are twofold ; either we conclude on the contempora- 

 neity of strata at a distance from each other on the sole ground of 

 real or supposed identity of species, or vice versd^ we maintain that 

 they are not contemporaneous, because they contain a certain pro- 

 portion of different species. The conclusion may possibly be correct 

 in both cases, but the grounds on which it rests are not necessarily 

 sufficient. We have only to examine the existing faunas round the 

 coasts of Europe and in the Arctic Seas to be struck with the remark- 

 able difference in their contents. Even the shores of our own island 

 at no great distance from each other present very great divergences of 

 typical forms, dependent no doubt on numerous extraneous agencies, 

 many of which we can ourselves detect, but of which many have as 

 yet escaped our notice, and will probably continue to do so for ages 

 to come. Why then should we not admit the same phsenomena in 

 former ages ? why must we necessarily jump at the conclusion that, 

 because different strata contain different species, they must belong to 

 different periods ; or vice versa, that because they contain the same 

 species, they belong to the same period ? Local features and local 

 phaenomena may account for this difference or identity. Nor can we 



