248 REPORT OF NATIONAL MUSEUM, 1892. 



reader is familiar with and accepts as trustworthy those which they 

 have adopted for their own guidance. 



If it were not for my evident need of frequent reference to such 

 elementary matter the desirability of publishing it in this connection 

 might perhaps be questioned by those who are already familiar with 

 it and with the range of its applicability. Still, the working geologist 

 needs only to recall his early embarrassments and later experiences to 

 be assured that the time has not yet passed when even the frequent 

 enunciation of elementary truths is of material benefit to the student. 

 I not only have not hesitated to adopt such a treatment of the subjects 

 of these essays, but I have not sought to avoid numerous trite remarks 

 and commonplace statements. These, however, are employed not so 

 much for the purpose of conveying information as for that of giving 

 logical continuity to the statement of my own ideas and of leaving the 

 least possible room for doubt as to my meaning. 



The relation of biology to geological investigation is so fundamental 

 and the facts pertaining to it are so concrete and so accordant with 

 both biological and physical laws, that the prevalence of any opposition 

 to its legitimate claims seems unnatural. It is also unnatural that 

 claims should still be made in favor of that relation which are not sup- 

 ported by the principles of modern biology. Of late years, however, 

 such wide differences of opinion have become prominent, some of them 

 being especially so among American geologists. In their writings 

 some of these authors either entirely ignore biological evidence as 

 furnished by fossil remains or treat the best of it as being of little 

 importance in the investigation of structural geology. Others have 

 taken quite opposite ground, not only making the just claim that 

 biological evidence is indispensable in structural geology, but the 

 untenable one that it is absolute and exclusive in systematic geology. 

 Notwithstanding the prevalence of these extreme views, I have ab- 

 stained from a controversial attitude in the treatment of the subjects 

 to which they pertain, preferring to attempt their statement in such a 

 way that the reader will necessarily reach correct conclusions. 



Because it is necessary to discuss those differences of opinion in these 

 essays, it is desirable to refer briefly to their origin and the causes of 

 their perpetuation. Doubtless some of the causes of their existence 

 are remote or obscure, but it is apparent that they are largely due to 

 the broadening of the field of geological investigation, making it neces 

 sary that it should be divided into numerous specialties. In such cases 

 it is natural that differences of opinion should be greatest between 

 those investigators whose chosen studies are most diverse in character. 

 Another cause is doubtless one of inheritance from the early condition 

 of both geological and biological science. 



A special cause of the perpetuation of these extreme views evi- 

 dently exists in the form of personal domination by such of those who 

 entertain them as happen to possess unusual opportunities for their 



