Professor Ramsay'' s Address, 513 



gradual and contmuous changes ; and these imperfectly understood 

 phenomena have induced a half intuitive and growing belief that the 

 laws, both physical and biological, that govern the world are quiet, 

 progressive, and unviolent. 



Proceeding now a point further, the connection of life with the 

 modifications which have taken place in the crust of the earth some- 

 what helps us in our endeavours to understand the question. As 

 every one knows, there have been great numbers of different genera 

 and species inhabiting the world at different geological epochs, the 

 remains of which lie buried in the various formations ; and looked 

 at on a large scale, and over broad areas, it is evident that there has 

 been a succession of life, each of the greater series of formations 

 being more or less marked by their own particular fauna. This fact 

 led to the old geological doctrine that there had been many sudden 

 creations, by which the world was at various times peopled, that 

 these inhabitants, after long intervals, were as suddenly destroyed, 

 that new creations came in, and that each formation was in this wslj 

 marked by its peculiar forms of life. When, however, it was found 

 that in some formations a few, or sometimes many, of the same 

 species were common to two or more formations, this theory of 

 complete and sudden extinction and creation was seen to be 

 untenable. By and by, when the geological structure of Britain 

 began to be minutely analysed, it was found in cases of uncon- 

 formable stratification, even when the upper formation was in time 

 the next Jcnoion member of the series to that which lay below, that 

 breaks in the succession of marine life, partial or total, always 

 accompanied such unconformities in stratification. It has, indeed, 

 been a question with some geologists whether two marine faunas, 

 commonly recognised as belonging to two distinct and far apart 

 geological epochs, such as the Silurian and Carboniferous, could not 

 have been contemporaneous in past eras, or indeed even now. It is 

 very possible that something of this kind may have been the case ; 

 but in my opinion only in a mixed and minor way between periods 

 or formations that in a geological sense were not far apart in time. 

 When we consider the greater formations, such as Silurian and 

 Carboniferous, Oolitic and Cretaceous, the probabilities, as I have 

 elsewhere argued, are almost infinitely against this assumption, for 

 if so, for example, an Oolitic fauna in whole or in part might both 

 underlie and overlie Cretaceous formations. But, however we may 

 look upon this question, it is certain that the great principle of a 

 succession of Kfe, showing a method of change and progress, the old 

 disappearing, and the new coming in, and breaks in succession of life, 

 as I have shown in detail elsewhere, have a close connection with 

 unconformability of strata, and gaps in geological time unrepresented 

 by stratified formations over areas of varying size, such areas being 

 determined by those agents that produced upheaval and denudation 

 of continents and islands. 



I could follow out this view with particulars, but without now 

 doing so this reasoning seems to assure us that there never has been 

 universally over the world auy complete destruction of life, but that 



VOL. III. — NO. XXIX. 33 



