3H 



University of California. 



[Vol. i. 



INTRODUCTION. 



Inapplicability of European Standards. — Geology was first stud- 

 ied in Europe; and the divisions and subdivisions of the rocks 

 and of time were based on the great unconformities of the rock- 

 system and the great changes of the life-system observed there. 

 When investigations extended to other countries, naturally, similar 

 divisions were looked for and apparently found. Closer study, how- 

 ever, soon showed that the correspondence was not complete for 

 America, and seemed to fail entirely for India, Australia, and Africa. 

 The tendency, therefore, in recent years has been to seriously doubt 

 whether there are any divisions which apply to all places; whether 

 we should not give up trying to write a general history of the whole 

 earth; whether the history of each continent must not be studied 

 for itself. There seems to be a real danger of opinion going too 

 far in this direction. It has been proposed, therefore, that this ques- 

 tion be discussed by this Congress of Geologists. 



It will be admitted that for a comprehensive view of any subject 

 some knowledge of the history of thought on that subject is neces- 

 sary. First, then, a few words on this history. 



Early Views. — -In the early part of the present century, events of 

 geological history were supposed to be not only removed from 

 direct observation, but so different from anything now occurring 

 that exact reasoning on them based on observation of causes now 

 in operation seemed hopeless. The construction of the history of 

 the earth by interpretations of its structure seemed, therefore, a 

 legitimate field for the exercise of the scientific imagination. Hence 

 it was that unconformities of strata associated with sweeping and 

 apparently sudden changes of life-forms were naturally attributed 

 to violent and destructive convulsions of the earth's crust and whole- 

 sale exterminations and recreations of all life-forms. Geological 

 history was a succession of catastrophes, each inaugurating a new 

 era, which remained substantially unchanged until another catas- 

 trophe. This view was in full accord with the then prevalent doc- 

 trine of the supernatural origin of new organic forms and the per- 

 manency of specific types, and regarded as a strong confirmation of 

 the latter. Geology was not yet a science in the proper sense of 



