DEVELOPMENT OF UNIFORMITARIANISM. 67 



esis is ever diniinisliing and tlie trustworthiness or exactitude of the 

 science constantly increasing. 



Such is the stage of reasoning through identity in succession or lio- 

 mogeny. It may he called the stage of genetic chissification or the stage 

 of uniforinitarianisni. The concomitant intellectual processes are a just 

 comhi nation of deduction and induction, of evolutionary and involu- 

 tioiuiry reasoning, and knowledge at once expands and imi)roves, in- 

 creasing constantly in exactitude as well as in extent. The stage has 

 fully come for stratigraphy, for gradation (or that hranch of dynamic 

 geology which deals with i)articlc movements), and for paleontology ; 

 but it has not yet come for that branch of dynamic geology which deals 

 with mass movement in the earthcrust. 



THE HERITAGE OF HYPOTHESIS. 



During the earlier stages in the growth of geologic science, when the 

 observing faculty was ill trained, and when students reveled in florid 

 speculation based on scant observation of the rare and remote, two note- 

 worthy hypotheses sprang from analogic reasoning and gained wide 

 acceptance : one was the hypothesis that rivers flow in catastroi)hic frac- 

 tures in the earthcrust; the other the hypothesis that the great features 

 of the globe were produced b}^ lateral stresses and movements in the 

 earthcrust due to shrinking of the nucleus of the planet. Now that ]K)th 

 hypotheses have been tested by comparison with facts and by more ad- 

 vanced reasoning, it is seen that they had much in connnon. Both 

 appealed to the unknown in nature ; ])oth ignored the daily procession 

 of events in the degradation of the land and the rhythmic rise and fall 

 of shores; both represented rude analogy between things unlike in kind 

 and magnitude, for in both cases the analogy was found in the fracture 

 or deformation of small bodies unlike the earth in constitution. In so 

 far as they "svere based on fact, both hypotheses rested on the aberrant 

 rather than the normal, the local and exceptional rather than the gen- 

 eral; and while they were measurably and temporarily useful in stimu- 

 lating thought, l)oth diverted attention from the facts of nature and 

 therel)y tended in some degree to retard the progress of knowledge. No 

 man ever saw a great valley formed by fracture of the earthcrust, nor 

 did man ever observe a lateral movement in the earthcrust (save possi- 

 bly in connection with a dominant vertical movement), though all men 

 saw or might have seen the endless activity of the streams in excavating 

 valleys, the endless vertical oscillations about the shores of the Mediter- 

 ranean, North sea, the l)ay of Bengal and Aral)ian gulf; yet in the dim 

 light of dawning earth-science the actual processes were overlooked and 



