INTERNATIONAL GEOLOGIC INSTITUTE S97 



of some geologists there are no natural divisions that hold 

 good beyond limited provinces. They recognize no general 

 divisions of a sufficiently definite kind to serve the purposes of 

 a concrete classification. In their judgment the succession of 

 geologic events was a continuous progression. They admit that 

 it was differentiated locally and even continentally, but not so uni- 

 versally as to furnish a good basis for classification. They rec- 

 ognize that the existing classifications are natural in some degree 

 as applied to Europe and America, the regions upon which they 

 have been founded, but they anticipate that they will prove quite 

 arbitrary as applied to other continents and to the world as a 

 whole. Entertaining these fundamental views, they hold that 

 classification should be regarded merely as a convenient arbitrary 

 device, and that the existing systems should give way to a more 

 convenient one, much as the old systems of measurement are giv- 

 ing way to the metric system. 



On the other hand, there are those who regard the history of 

 the earth as naturally divisible into important stages whose rec- 

 ognition constitutes a leading function of philosophic geology. 

 None of these contend that there was at any time a universal 

 cessation of sedimentation or a complete break in the continuity 

 of life. They freely admit and affirm that there is a fundamental 

 continuity, but at the same time they hold that progress was not 

 uniform, but pulsative or rhythmical. Specifically, speaking for 

 some of these, they think they find periods of stress-accumula- 

 tion followed by periods of stress-relief, periods of land-expansion 

 followed by periods of sea-transgression, periods of topographic 

 accentuation followed by periods of base-leveling, periods of 

 climatic uniformity followed by periods of climatic diversity, 

 periods of biologic luxuriance followed by periods of biologic 

 impoverishment, in short, a pulsative progress whose successive 

 phases furnish a natural basis for classification. 



The existence of these diverse views is an expression of the 

 imperfection of present knowledge. Were exhaustive data at 

 command it could be determined whether the dominant character 

 of the earth's progress was uniformity or periodicity, and hence 



