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SCIENCE. 



LN. S. Vol. XVI. No. 4U0. 



held more firmly to fact as a basis for induc- 

 tion than Darwin; but also, no man has 

 more successfully projected by deduction 

 beyond his facts than Darwin. This in 

 biology was a task of extraordinary difficul- 

 ty. In geology one who has a firm grasp 

 of the principles of physics and chemistry 

 may be more daring. Their principles, if 

 not more definite than the laws of biology, 

 are at least better known and more simple. 

 Therefore, one, after having observed the 

 facts in a district and grasped the princi- 

 ples which explain them, may deduce what 

 are likely to be the facts in the field and 

 their relations in advance of observation. 

 Or more concretely, after one gets the cor- 

 rect idea as to the meaning of the phenom- 

 ena for a certain district, he often can tell 

 in advance of observation what he will see ; 

 or can find what I call ' geology mude to or- 

 der. ' 



There is no better or more severe test of 

 a theory than one 's capacity to find geology 

 made to order. If observation of the area 

 where the facts are expected to be found in 

 a certain way shows that nature does not 

 obey the order, this is certain evidence that 

 one or more factors in the problem have 

 been omitted and that the theory is inade- 

 quate. In so far as the theory is adequate, 

 the geology will be found as anticipated. 

 The reason for this is the very great com- 

 plexity and delicate adjustment of the phe- 

 nomena of nature. To illustrate, if the 

 many parts of some complex machine, such 

 as a Hoe press, or a chronometer, were scat- 

 tered far and wide, and then one should 

 gather some of these parts, and try to fit 

 them, he might find that a certain set fit 

 perfectly. If this were so, he would know 

 to a certainty that these parts are in the 

 correct positions and relations, even if he 

 did not know the relations of these parts 

 to other parts or the purpose of the whole ; 

 for so complex and exact is the adjustment 

 that there is but one way to put the parts 



together. Another set of parts might be 

 found and these made to fit. But doubtless 

 certain parts would not be found. These 

 would be missing links necessary to make 

 a perfect machine. In this situation, if the 

 man had a genius for mechanical construc- 

 tion, and an insight into principles, he 

 might be able to understand the purpose of 

 the whole, and finally to supply the parts 

 which render the whole a useful machine. 

 This he would be able to do just in propor- 

 tion as he had mechanical insight. 



So the geologist fits together his numer- 

 ous diverse facts. If he finds a solution of 

 his problem which gives accordance to all 

 the numerous facts observed, he may be 

 sure he is on the right track, even if he is 

 incapable of seeing the full truth, for so 

 delicate is the adjustment of facts that 

 where they are numerous there is usually 

 only one way to put them together. Just in 

 proportion as the man has a working knowl- 

 edge of the principles of physics and chem- 

 istry and biology, and the other cognate 

 sciences will he be able to eliminate er- 

 roneous explanations, combine the facts into 

 groups under true theories, and correctly 

 infer how the dift'erent groups are to be ad- 

 justed, how the various facts which seem at 

 first to have no definite relations are relat- 

 ed. Or, to put it in another way, in propor- 

 tion as he knows the rules of the game will 

 he be able to correctly interpret the mean- 

 ing of phenomena and from them to project 

 into the unknown. The importance of un- 

 derstanding the rules of the game is not 

 often appreciated. To the person who is 

 ignorant of the principles of the various 

 sciences all things are possible. So many 

 wonderful things have happened within the 

 past half century that he thinks it possible 

 for anything to happen. He has no prin- 

 ciples by which he can determine whether 

 or not a statement is probably true. Hence 

 all sorts of grotesque notions flourish. In- 

 deed, the very fact that so many wonderful 



