EVOLUTION AND THEISM. 401 



volcanic action and in the metamorphism of sedimentary rocks ; 

 showing these to be the mechanical results of such inequalities of 

 the rate of cooling of different parts of the surface, as may well be 

 conceived to arise from the conditions of the previous conden- 

 sation. The other, leading us backward from the present to the 

 past, brings the various agencies which we know to be at present 

 modifying the earth's surface to bear upon its previous history ; 

 enabling us " in the fall of rain and the flow of rivers, in the 

 " bubble of springs and the silence of frost, in the quiet creep of 

 " glaciers and the tumultuous rush of ocean-waves, in the tremor of 

 " the earthquake and the outburst of the volcano, to recognize the 

 "same play of terrestrial forces by which the framework of our 

 "continents has been step by step evolved." (Geikie.) 



I cannot suppose any one I am now addressing, to be ignorant 

 of the doctrine as to which modern geologists are now, I believe, 

 in universal accord — that of continuity of change (not necessarily 

 of uniformity in its rate) throughout the entire period of the 

 earth's history. The old notion of universal interruptions has 

 given place to that of local changes analogous to those of which 

 we have present experience ; that of vast sudden convulsions, to 

 slow progressive elevations or subsidences. The regular succes- 

 sion of stratified deposits, while interrupted in one portion of the 

 earth's surface, is found to be completed in another. And the 

 same proves to be the case in regard to the succession of those 

 organic forms, whose remains are preserved to us in those deposits. 

 For palaeontologists have long since been forced, by the " logic of 

 facts," to abandon the idea that in each of the successive 

 " periods " marked out by the earlier stratigraphical geologists, 

 the earth was peopled by a set of plants and animals peculiar to 

 that period — many of these forms being traceable with certainty, 

 in the same spot, from one " formation " to another ; whilst, when 

 they disappear in one locality, they may often be found to have 

 migrated to another. And thus, before the introduction of the 

 Darwinian doctrine, the old notion of a succession of entirely new 

 creations of Plants and Animals, to replace the Floras and Faunas 

 which had, one after another, been swept away from the entire 

 surface of the globe, was giving place to the notion of continuous 

 succession — certain species dying out from time to time, as they 



