6o4 CHARLES R. VAN HISE 



importance. The causes offered to explain the phenomena do not 

 exclude one another. It is believed that each of them is a real cause, 

 and partly explains the phenomena — that the different causes are 

 complementary. While a majority of geologists have been content with 

 suggesting a single physical cause for a phenomenon, others have taken 

 more than one possible cause into account. Thus Chamberlin^ has 

 formally adopted the method of multiple hypotheses. But the great 

 majority of those who have considered more than one hypothesis in 

 connection with a geological problem have carried on their discussions 

 as if one of the suggested causes must be selected to the exclusion of 

 the others. 



As a matter of fact, almost every complex geological phenom- 

 enon has not a simple, but a composite, explanation. To illustrate, 

 in Chamberlin and Salisbury's text-book of geology it is stated 

 that the explanation of volcanism may be given upon the assump- 

 tion that the lavas are original; or, second, on the assumption 

 that the lavas are secondary. Under the first assumption it is sug- 

 gested (i) that lava outflows from a molten interior, and (2) that 

 lavas flow from molten reservoirs. Under the second assumption 

 it is suggested that lavas may be assigned (3) to the reaction of water 

 and air penetrating to hot rocks, (4) to relief of pressure, (5) to melt- 

 ing or crushing, (6) to melting by depression, and (7) to the outflow 

 of deep-seated heat.^ At the close of the discussion it is said that 

 these hypotheses "must be left to work out their own destiny. "^ 

 I fear many will make the inference, although I have no idea that 

 the authors so intended, that one among these hypotheses will be 

 victorious in the struggle for existence and the others totally over- 

 thrown. My point in this connection is that the two main supposi- 

 tions, and all of the hypotheses under them, may be true in' part; 

 that these various explanations are not necessarily exclusive of one 

 another, but may be supplementary. When we have a quantitative 

 discussion of the probable effects which may be expected from each 



1 T. C. Chamberlin, " The Method of Multiple Working Hypotheses," Journal 

 OF Geology, Vol. V (1897), pp. 837-48. 



2 Chamberlin and Salisbury, Geology, Vol. I, "Processes and Their Results," 

 1904, PP- 595-602. 



3 Ihid., p. 602. 



