1894- CONTINENTAL GROWTH. 339 



this occurred in the past ? If we ascertain correctly, it will be the 

 key to the future — a truly geological prophecy. That there is a rela- 

 tion of cause and effect between subsidence, sedimentation, and sub- 

 sequent upheaval, it has been my object to point out in the " Origin 

 of Mountain Ranges." In development of this idea, I seek to show 

 how, as a consequence of this action and interaction, the earth's 

 strata come to be divided into rock-groups containing distinguishing 

 fossils and having each its characteristic lithological grouping, which 

 we know as Periods. 



If a great group of physical features lasts throughout vast eons 

 of time, such as I have shown has happened even during the Quater- 

 nary period (which we are living in now, and which is likely to 

 continue much longer), it is evident that the deposits will have a 

 characteristic lithology — looked at in the large way — and a fossiliferous 

 facies will distinguish them from the Tertiary and preceding rock- 

 groups. Representatives of the modern mollusca and the vertebrate 

 and mammalian fauna and of the modern flora will be here and there 

 embalmed to give further distinction to the strata and joy to future 

 geologists. Among these fossils, works of art and fragments of ships, 

 together with bricks and clinkers from ocean steamers, such as even 

 now are occasionally dredged up in the Atlantic, will be a feature. 

 I understand that when soundings come up with cinders attached 

 to them the heart of the mariner rejoices, knowing that he is 

 on beaten tracks, if so inappropriate a phrase is allowable in ocean 

 navigation. Truly, if the world continueth through another geologic 

 period, and there seems no reason to assume that it will not, as 

 the internal forces are still alive making for rejuvenescence, the 

 Quaternary will be the most distinct and remarkable period of all. 

 Not only will the remains of man and his works up to the present be 

 embalmed, but also those works still in the potentialities of the future 

 to which we may, considering the progress of the last fifty years, look 

 forward with mysterious expectation, if not awe. The future great 

 period will include the present and terminate with the completion of 

 the Quaternary. 



Sediments of Existing Seas. 



If the preceding reasoning has any cogency in it, there must 

 exist on our coasts, at the mouths of the great continental rivers, 

 enormous sedimentary deposits laid down since the close of the 

 Tertiary. The denudation of the land since then, though late in 

 geologic time, has been enormous. Whole areas have been stripped 

 of their Tertiary covering and in mountain districts thousands of feet 

 of strata removed. To go no further than our own isles, the Tertiary 

 rocks that remain are but a fragment of what once existed. 



The Miocene rocks of Antrim, Staffa, Eigg, Rum, and Skye 

 consist chiefly of lava flows and ashes of great terrestrial volcanoes, 

 which fill up the undulating valleys of the Chalk in Antrim, and those 

 of Oolite and Silurian gneiss in what is now the West of Scotland. 



z 2 



