DIASTEOPHIC AND PALEONTOLOGTC EVIDENCE 297 



like the Eockies, the Pyrenees, the Alps, the Himalayas, have not been 

 coincident in time. Similarly it remains to be shown that great coastal 

 movements, such as those of America and Europe in Tertiary time, were 

 coincident. Many are certainly known not to be coincident, and it fol- 

 lows that at least a very large percentage of disconformity and uncon- 

 formity is not diastrophic in the l)road sense in which the term is properly 

 used. 



On the other hand, the progressive and retrogressive evolution of ani- 

 mal and plant types on the two continents, or even on the four continents, 

 presents a most impressive ai-ray of precisely or closely similar coinci- 

 dences of precisely or nearly similar events in time. If any great or 

 striking discords could be demonstrated between the rates of evolution of 

 animals and of plants of similar descent in different continental areas 

 then correlation through paleontology would largely break down; but 

 uniform rates of evolution of organisms of similar ancestry even where 

 widely separated geographically is the prevailing law, notwithstanding 

 that there are exceptional cases both of retardation and of acceleration. 



It is absolutely necessary that those geologists who base their time de- 

 terminations on appeals to the diastrophic theory should establish their 

 first premise, namely, that the actual or alleged movements in America 

 were coincident in time with similar diastrophic movements in Europe 

 and Asia. 



In the present Jurassic-Cretaceous problem it is necessary for the ad- 

 herents of the diastrophic system of correlation to prove that large and 

 coincident earth movements on both sides of the Atlantic marked the 

 boundary between Jurassic and Cretaceous time. First, that at the close 

 of the Jurassic a movement of elevation expelled the sea from the Eocky 

 Mountain region, and that following this in Lower Cretaceous time a 

 submergence took place. Second, that in England, where the close of the 

 Jurassic and beginning of the Cretaceous was first clearly defined by 

 paleontologists, a diastrophic movement took place during or immediately 

 after the Purbeckian, Third, that in other parts of the world there are 

 similar diastrophic boundaries between the Jurassic and Cretaceous. 



To take but a single illustration : if we glance at the schematic section 

 of the relations of the Jurassic and Cretaceous in AYiltshire, England, 

 we find an entirely different set of conditions than those demanded by 

 the diastro])hists; not even the first condition is fulfilled, for the Jurassic, 

 with its closing successive stages — the Kim.eridgian, Portlandian, Pur- 

 hecl'ian — passes gently and without marked change into the Wealden. 

 There may be some disconformity; there is no angular unconformity. 

 Only after the time interval between the Jurassic and Cretaceous has 



