(]0 GRAND CANON DISTRICT. 



lignites, fossil leaves, and carbonaceous shales oft he whole Cretaceous 

 system, the brackish-water fossils of the lowest Tertiary, leave no doubt 

 as to the verity of the foregoing inference. The final restoration, then, 

 of the strata to their original positions leaves them horizontal.* 



If we draw a section of the strata restored to horizontality, we shall 

 find that the strata now remaining require, in order to perfect their con- 

 tinuity, the restitution of large masses fully equal to those which we have 

 inferred to have been swept away by erosion. Any hesitation to do 

 this would leave us without resource. Any other hypothesis, so far as 

 lean conceive, would be not only without support in the l'acts pre- 

 sented, but in opposition to their entire tenor and purport. 



The geologist who is familiar through long lield-study with the ph\ s 

 ical problems presented in the West would not need further argument 

 to become satisfied of the reality of the great erosion here inferred. 

 Perhaps he would consider that too much has been said in support of 

 it already; especially since the subject of this paper is not the San 

 Rafael but the Grand Canon district. But I have devoted so much dis- 

 cussion to the San Rafael district because it is a type of a congeries of 

 districts which make up the Plateau Province, and because it exemplifies 

 in the most intelligible, compact, and complete manner the broad facts 

 and laws which are to engage our attention hereafter. These facta and 

 laws apply to the Grand Canon district; but to take the facts there 

 presented and arrange them in a clear view before the mind of one who 

 has never visited that region, and make them definite and convincing, 

 would be extremely difficult without preparatory exercises on problems 

 similar in kind but simpler iii form. For this reason 1 propose, before 

 leaving the San Rafael district, to bring out another category of facts 

 which it exemplifies. They involve a generalization very interesting in 

 itself, and of the greatest utility in solving many problems presented in 

 all parts of the Plateau country. This generalization— or law in the 

 sense of an observed order of facts— may be called the Persistence oj 

 Rivers. 



The rivers of the Atlantic States, from the Hudson southward, cut 

 through the Appalachian ridges by narrow gorges, or gaps, which seem 

 to have beeu quarried out for the purpoes. Geology, however, does not 



*It would bo very instructive, if space permitted, to elaborate this discussion of the 

 original horizontality, and I am tempted to point out in the hastiest manner some 

 obvious consequences of the deduction. It appears that if this deduction be true 

 the deposits must have settled or subsided as rapidly (iu the long run) as they wen 

 accumulated. The surface of deposition appears never to have varied much from sea 

 level. But the total accumulation of Permian, Mesozoir, and Tertiarv beds was nearly 

 11,000 feet, and when the deposition ended (supposing that it ended in the Middle 

 Eocene, though I think it more probably continued here until the close of the Eocene) 

 the Permian must have sunken more than two miles below sea-level. The gradual sub- 

 sidence of largo bodies of sediment as they accumulate in strata is a fact now generally 

 recognized, and is of universal application. That it is caused by the gross weight of 

 the enormous masses of deposited material sinking into the yielding earth seems a 

 most natural explanation. 



