670 W. M. DAVIS 



It is the active appeal to observation that has checked the freedom 

 of speculation which our brilliant predecessors enjoyed in an earlier 

 century, when their fanciful schemes were little restrained by the 

 barriers of fact that have since then been built up on every side. 

 Indeed, schemes came to be for a time so much in disrepute that 

 some investigators wished to suppress theorizing altogether, as was 

 seen in the effort to supplant the name "geology" by "geognosy." 

 I rejoice that the effort did not succeed; for if earth science were 

 really limited to facts of direct observation, it would be at best a dreary 

 subject. 



How uninspiring would be such a knowledge of tides as could be 

 gained only by actual observation along the seashore! A collection 

 of such records would be an orphanage, where the foundlings would 

 doubtless be well cared for and thoroughly drilled in their little duties, 

 and yet left without the inspiriting, enlarging influence of parental 

 care that they find on adoption into the family of earth, moon, and 

 sun. 



Whatever the danger of schemes and theories, they give the 

 best of life to our bodies of facts, and our science cannot survive 

 without them. Indeed, we have come to know that the danger of 

 systems and theories lies, not in their dependence on the imagination, 

 but in the possibility of their careless growth and of their premature 

 adoption, and even more in the acceptance of a personal responsi- 

 bility for their maintenance, instead of leaving that responsibility to 

 external evidence. 



If there is any subject in which the aid of schemes and theories 

 based on observations has been absolutely necessary for progress, 

 it is earth science, where so many of the essential facts are invisible. 

 It cannot be too carefully borne in mind that observation and theory 

 are alike in their objects, however different they may be in their 

 methods. Both seek to discover the facts of their science. One 

 deals with facts that are visible to the outer eye ; the other, with facts 

 that cannot be seen, either because they are too small or too large for 

 outer vision, or because they are hidden within the earth or in past 

 time, or because they arc impalpable abstractions or relations. In 

 both, fancy is sometimes taken for fact, more often so perhaps in 

 theorizing than in observing; but we must not for that reason give 



