482 SCIENCES OF THE EARTH 



one of them may survive, since it often proves in the end that several 

 agencies were conjoined in the production of the phenomenon. Hon- 

 ors must often be divided between hypotheses. In following a single 

 hypothesis, the mind is biased by the presumptions of the method to- 

 ward a single explanatory conception. But an adequate explanation 

 often involves the coordination of several causes. This is especially 

 true when the research deals with complicated phenomena such as 

 prevail in the field of the earth-sciences. Not only do several agencies 

 often participate, but their proportions and relative importance vary 

 from instance to instance in the same class of phenomena. The true 

 explanation is therefore necessarily multiple, and often involves an 

 estimate of the measure of participation of each factor. For this the 

 simultaneous use of a full staff of working hypotheses is demanded. 

 The method of the single working hypothesis is here incompetent. 



The reaction of one hypothesis upon another leads to a fuller and 

 sharper recognition of the scope of each. Every added hypothesis is 

 quite sure to call forth into clear recognition neglected aspects of the 

 phenomena. The mutual conflicts of hypotheses whet the discrimin- 

 ative edge of each. The sharp competition of hypotheses provokes 

 keenness in the analytic processes and acuteness in differentiating 

 criteria. Fertility in investigative devices is a natural sequence. If, 

 therefore, an ample group of hypotheses encompass the subject on 

 all sides, the total outcome of observation, of discrimination, and of 

 recognition of significance and relationship is full and rich. 



Closely allied to the method of multiple working hypotheses is 



The Method of Multiple Series 



In many of the more complex problems of the earth-sciences the 

 basal facts are but imperfectly determined, e. g., the rate of rise of 

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

 ductivity of the earth's interior, the amount of the earth's shrinkage, 

 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 cannot range beyond 



