36 IOWA GEOLOGICAL SURVEY 



to decipher, or as the blocks with which he has to construct his 

 temple of truth. Industriously to seek out his building stones, 

 assemble them, and fit them deftly together, that is his proper 

 function. Just as in the physical sciences the chief work to 

 be done is observation and experiment, since from these alone 

 conclusions can be drawn; so also in the natural history of the 

 past the first duty of the worker is careful investigation before 

 he may offer a presentation of results. It is incumbent upon 

 him equally with the historical student to ' ' expend all diligence in 

 discovering and investigating all possible material, and after this 

 has been done, to examine it with rigorous critical acumen." 

 Enormous and bewildering as may be the task of assembling the 

 material, the collection of facts is but preliminary to research 

 of really useful character ; facts must be reduced to orderly sys- 

 tem, results must be combined, many phenomena included under 

 one law, and many subordinate laws under one more compre- 

 hensive, before we can gain approximate understanding, or be- 

 fore judgment can be passed on knowledge. The method of 

 both physical and natural science, as has been said, is to draw 

 conclusions from known and recorded phenomena ; and the ulti- 

 mate object of each is to widen knowledge and deepen our 

 understanding. Especially is the mind of the naturalist alert to 

 grasp general principles involved amid the multiplicity and com- 

 plexity of phenomena; by training he acquires a vivid sense of 

 relations; it is instinctive with him for the part to suggest the 

 whole ; his intellect leaps from the specific instance to an appre- 

 hension of the general law; and finally his generalizations attain 

 significance through the clarifying agency of "reorganizing 

 ideas". 



By reorganizing ideas we mean those great and illuminating 

 conceptions that enter the world of thought at propitious mo- 

 ments and are sometimes epoch-making for the progress of 

 science. "Emancipating conceptions" they are called by some, 

 idees directrices is the corresponding French term. "That 

 which usually forms a grand conception," says Montesquieu, 

 in portraying their influence, "is a thought so expressed as to 

 reveal a number of other thoughts, and suddenly disclosing what 

 we could not anticipate without patient study." If we may be 



