METHODS OF THE EARTH-SCIENCES. 71 



internal temperature, the rigidity of the earth's body, the thermal con- 

 ductivity of the earth's interior, the amount of the earth's shrink- 

 age, the extent of lateral thrust in the formation of folded mountains 

 and many others, indeed most others. There is need to deal with 

 these problems notwithstanding the imperfection of the basal data, for 

 in many cases these must long remain imperfect. Moreover, there is 

 need to treat these problems tentatively to determine what funda- 

 mental facts are really needed, how these can best be secured, and with 

 what precision they must be determined. Preliminary trial may save 

 much tedious and expensive experimentation. It is as foolish to culti- 

 vate sterile soil in science as in agriculture, and preliminary tests may 

 show that given soils are necessarily sterile. In many cases, all the 

 needs of the problem may be met by a multiple series of assumptions 

 covering the full range of a probable fact. In most cases it is easy to 

 see that the value of a given fundamental factor can not range beyond 

 certain extremes on either hand. If a series of values ranging from 

 the one extreme to the other be used simultaneously in the inquiry, the 

 full range of results dependent on this factor may be covered. In some 

 inquiries this serves as well as if the exact truth were known, for what- 

 ever the assignable value, certain deductions Can not stand. In other 

 cases, it will be shown that a very slight change in the value of the 

 basal factor will wholly change the outcome, and hence that extremely 

 accurate determinations must be made before any trustworthy solution 

 can be reached. Expensive determinations in the first case are folly; 

 very accurate determinations in the second are to be sought at any cost. 

 Conclusions on imperfect data in the one case are perfectly safe; con- 

 clusions without precise determinations in the other are folly. It is to 

 be hoped that, with the wider adoption of the method of multiple 

 series, tables of serial determinations covering the data of the more 

 vital phenomena of the earth-sciences will be constructed, as tables of 

 physical constants now are. 



The Method of Regenerative Hypotheses. 



In the method of multiple hypotheses, the members of the group 

 are used simultaneously and are more or less mutually exclusive, or 

 even antagonistic. Supplementary to this method is the use of a 

 succession of hypotheses related genetically to one another. In this 

 the results of an inquiry under the first hypothesis give rise to the 

 assumptions of the succeeding hypothesis. The precise conclusions of 

 the first inquiry are not made the assumptions of the second, for the 

 process would then be little more than repetitive, but the revelations 

 and intimations, perhaps the incongruities and incompatibilities of the 

 first results beget, by their suggestiveness, the basis of the second. 

 The latter is the offspring of the former, but between parent and 

 offspring there is mutation with an evolutionary purpose. A cruder 

 first attempt generates a more highly organized and specialized work- 



