No. 554] ADAPTATION IN LIVING AND NON-LIVING 75 



little or no visible water. Let us suppose that interest 

 was at that time aroused in the distribution of pumiee 

 pebbles upon certain areas of the dry valley floor, and let 

 us suppose that a previous migration of these, similar to 

 the one just described, was suggested as a possibility. 

 At that time the direct test by observation was not pos- 

 sible, but the whole question — as far as the floating adap- 

 tation is concerned — could have been settled readily 

 enough either by bringing water to the pebbles or by 

 taking some of the pebbles to water. But of course we 

 should have been dealing, in this instance again, with the 

 determination of the presence or absence of a certain 

 property in the pebbles, as related to a certain property 

 of water. 



In the vast majority of the cases of this sort that at- 

 tract our attention at the present time, however, natural 

 science is unable to obtain direct observational tests, even 

 of the experimental sort, and some indirect method of 

 comparison must be resorted to. Now, indirect methods 

 for determining the degree of a proposed adaptational 

 property consists in nothing more than the determina- 

 tion, by whatever means may be convenient, of the de- 

 gree to which this property exists in the object consid- 

 ered. Thus, without ever bringing water and pumice to- 

 gether, it is perfectly possible to establish the ability of 

 the latter to float, as by determining the comparative 

 weights of equal volumes of the two substances. 



From what has preceded it is suggested that every 

 passive adaptation that we may consider resolves itself, 

 upon adequate analysis, into a problem of the measure- 

 ment and quantitative comparison of qualities or proper- 

 ties of objects. If neither the direct experimental test 

 nor the requisite measurements can be carried out, then 

 the suggestion of an adaptation is no different from the 

 statement of any other problem for which no method of 

 attack has yet been devised. But it must be recognized 

 in this connection that the usual biological adaptation is 

 not always appreciated as a problem in comparative 



