XCH rttOCEEDlNGS OF THE GEOLOGICAL SOCIETY. [May I9II, 



a record of the physical factors which have been one of the im- 

 pelling causes of their evolution ? 



In this branch of enquiry, however, the palaeogeography of a 

 single region, even when it embraces a whole country whose past 

 geological conditions have been so varied and typical as our own, 

 is inadequate to the strain of all-embracing generalisations ; and 

 the study of a whole continent, or, better, of the world itself as 

 a whole, is essential before it will be possible to reach a true 

 conception of the physical machinery which has been operating in 

 evolution. 



A corresponding world-wide outlook is also requisite when we 

 wish to place in correct perspective the physical development of a 

 limited area in association with the evolution of the physical 

 features of the world as a whole. The more important strati- 

 graphical works, like those of Sir Archibald Geikie in Britain, A. de 

 Lapparent in Prance, and Chamberlin and Salisbury in America, 

 have summarised for us the world-geology of the different Periods, 

 from which we can obtain a general conception of the broad 

 outlines of the geography of large areas of the world at different 

 times. Salisbury and Willis for America, and de Lapparent for 

 the whole world, have endeavoured to express in the form of maps 

 the known geological facts that bear upon the geography of the 

 different Periods. Even here, however, there is the serious 

 handicap that two thirds of the earth's surface are covered by sea 

 and inaccessible to observation. 



But there is a vast amount of work still to be done in filling 

 in the details of even the land portion of these maps, and each part 

 so filled in will inevitably diminish the difficulties left in extending 

 the lines in the areas into which our observations do not or cannot 

 extend. It is only by work of this description, by obtaining a 

 fuller and deeper knowledge of the whole of the events recorded in 

 our strata throughout the world, that we shall ever approach the 

 solution of the larger and more fascinating problems of Geology. 



(11) Conclusion. 



In conclusion, we may sum up some of the main points which 

 have been touched upon. The History of the Earth, so far 

 as the Geologist is capable of following it through the geological 

 systems and formations, is a history of successive geographies, 

 and of the relations of those geographies to the living beings 

 which successively characterised them. In the reading and 



