STRATIGRAPHIC TAXONOMY 599 



The only statements in the above quotation that I am inclined to take 

 -exception to are contained in the last paragraph. I hold, namely, that con- 

 tinental deformations and crustal foldings disturb the isostatic equilibrium 

 of the earth in proportion to their vigor and extent. If the land is raised 

 by folding or weighted in any other manner, such part tends to settle 

 back; and if any continental basin is loaded with sediment, its synclinal 

 structure is likely to be accentuated. All such adjustments, I maintain, 

 must have some effect on the strandline. If one side of a land mass is 

 folded, the capacity of adjacent sea basins must necessarily be increased 

 and its waters withdrawn from that side of the land. On the opposite 

 side, however, increased submergence is likely to occur. If a continental 

 basin be deepened and submerged, it would necessarily cause sea with- 

 drawal elsewhere. This phase of the subject has been discussed at some 

 length in describing tilting of positive areas. (See pages 405 to 407 and 

 411 to 432.) The efficiency of our correlations in such cases depends 

 entirely on our ability to match an emergent stage here with a submer- 

 gent phase there. Correlations of distant occurrences are seldom easy, and 

 these are especially difficult. But there are ways of doing them which, 

 I believe, will finally lead to a degree of success scarcely hoped for now. 



Ehythm ii^ Recurrence op geological Phenomena 

 general discussion 



The endeavor to bring all the systems, and so far as possible the minor 

 groups, into at least approximate coordination is justified by the belief 

 that we may thereby determine and express something of the rhythm that 

 seems to regulate diastrophic movements. That these movements occur 

 in rsponse to very definite laws none will deny ; and that their operation 

 in past geologic ages was not merely casual, but that they progressed with 

 a regularity in which such factors as time and volume were sufficiently 

 prominent to establish a measurable rhythm in the recurrence of similar 

 conditions seems scarcely less reasonable. 



Of course, as time went on conditions changed. This earth is very 

 different from what it was at its beginning. But while our conception 

 of its primitive form is based almost entirely on pure inference the prob- 

 lems that go no farther back than the oldest fossiliferous rocks are far 

 more amenable to solution. Our inferences respecting the latter, accord- 

 ing to which the surface of the earth has by progressive modification 

 changed from an almost featureless even expanse to its present diversified 

 aspect, are grounded on a great and rapidly growing stock of observed 

 facts. 



