4 BIOLOGICAL SOCIETY OF WASHINGTON. 



Asia and Africa, the European standards were still found suffi- 

 ciently exact for at least general conclusions. Even in Eastern 

 North America the order of the formations and the types of 

 the fossils which characterize them are closely like those of 

 Western Europe, and in many cases the species are regarded as 

 identical. 



It was natural, then, that the conditions which were found to 

 have formerly prevailed in those regions where geology was 

 first studied should be held to have been the normal conditions 

 for the whole earth. Such were the opinions formed by the 

 earlier European geologists ; and their successors still hold the 

 European standard to be applicable to every region, and to every 

 condition of climate which the earth has known. The leading 

 idea which is embodied in this chronological scheme would, I 

 think, be fairly illustrated by a diagram which may be con- 

 structed by taking such a section of the geological formations as 

 is usually given in the text-books of geology, that of Dana's 

 Manual for example, and projecting a series of circular lines from 

 the boundary lines of each of its divisions and subdivisions. Let 

 this series of circles represent approximately the time-equivalent 

 of the geological column of formations and the assumed universal 

 definition of each of its subdivisions. 



It will of course be understood that such a diagram could not 

 be intended to illustrate the time ratios of the different epochs, 

 periods, and ages into which historic geology has been divided. 

 It has been suggested only to illustrate the rigid character of the 

 paleontological time-standard which European geologists have 

 erected for themselves, and which they seek, with the consent of 

 most of the geologists of other countries, to apply to the whole 

 earth, even in minute detail. 



It was formerly held that not only have all species of animals 

 and plants been specially created, but that a majority of them 

 became extinct during or at the close of each epoch ; and that 

 each period was closed with a universal catastrophe, by which 



