CLASS 'IFICA TTON. 93 



ing his measurements with those of the Beagle 

 survey, he was struck with their uniformity. 

 He tabulated all the measurements represent- 

 ing the summit edges of the plains; and the 

 tabulation proved to him that the elevation of 

 the land had gone on at a remarkably equable 

 rate over a north and south distance of at least 

 five hundred miles. 1 There is comparatively 

 little danger of throwing away effort in a well 

 directed classification. The danger lies in not 

 comprehending the vast significance of the 

 process both in actual investigation and in the 

 presentation of results, and in the lack of per- 

 sistent determination to exhaust its resources. 

 Darwin himself sometimes owed it to happy 

 accident that he did not overlook this powerful 

 instrument. 



Guided by deduction to the probable relation 

 of the distribution of volcanoes to that of coral 

 islands, and to the distribution of fringing and 

 barrier reefs and atolls in relation to each other, 

 he spent months in mapping them from the 

 descriptions of voyagers, surveying vessels, etc. 

 From the classification of a vast chaotic mass 

 of facts scattered throughout geographic and 

 geological literature, he extracted some of the 

 most important conclusions of his whole work 



1 Geological Observations, etc., p. 211. 



