PROGRESS IN THE NINETEENTH CENTURY 489 



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 like an orphanage, where the foundlings are 

 doubtless 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. 



Hence, 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, whether 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 are 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 up either means of investigation. We have learned 

 that both observing and theorizing must be carefully conducted: 

 and we have therefore replaced the earlier watchwords, "Go and 

 see," with the later ones, "See and think." 



We may still give praise to those who apply themselves chiefly 

 to gaining first-hand knowledge of observable facts, but we have 

 learned to give greater praise to those who, on a good foundation 

 of visible facts, employ a well-trained, constructive imagination 

 in building ingenious and successful theories which shall bring to 

 sight the invisible facts. We have been longest familiar with the 

 need of theory in those branches of our subject which have, by reason 

 of association with mathematical problems, traditionally employed 

 deductive methods in their discussion, as in earth-measurement; we 

 are least familiar with it in those branches that have until lately 



