100 GRAM) CANON DISTRICT. 



whatever, and indeed the Mount Logan mass is one of the thickest expo- 

 sures of Permian beds thus far discovered. The former extension of 

 this series over the entire district in full volume may therefore be re. 

 garded as proven. In the ease of the Trias the evidence is from this 

 point of view not quite so clear. South of the Vermilion Cliffs two or 

 three remnants of it have been seen. One lies in the Grand Wash, a 

 lateral valley joining the Colorado from the north just where it issues 

 from the lower end of the Grand Canon. Another has been recognized 

 by Mr. Gilbert under the protection of lavas in the gigantic; pile of 

 San FranciSCO Mountain. But in neither of them is the entire Triassic 

 series represented. These may be held to prove also the extension of 

 the Trias over the entire district, and they give no sign of any attenua- 

 tion in the beds preserved. But of the Jura and Cretaceous not a soli- 

 tary outlier has yet been detected at any considerable distance from 

 their principal terraces. As to these two later formations we can only 

 reason from general considerations. The Jura and Trias, wherever 

 found, appear to be merely different portions of one period of deposi- 

 tion; the physical conditions attending the accumulation of both appear 

 to have been almost identical. Nor have we any reason to doubt that 

 the same considerations apply to the Cretaceous and Eocene. 



Still more forcibly is the same conclusion presented to us when we 

 come to the study of the faults and flexures. The Grand Canon district, 

 the High Plateaus, and indeed the entire Plateau country, has been 

 hoisted during Tertiary time far above the Sierra region lying west of 

 it. At the western border of the plateaus are found gigantic faults 

 where the strata have been sheared, and the country on the eastern 

 side presents beds lying thousands of feet higher than the continua- 

 tions of the same strata on the western side of the faults. These faults 

 have been studied, and the amounts of the displacements are very ap- 

 proximately known. Owing to the remarkably clear manner in which 

 all the facts are displayed, we are able, theoretically, to restore the 

 country to the position and configuration existing before these beds 

 were faulted and flexed. In this treatise, only the results can be given. 

 The discussion and treatment of the problem is too purely technical for 

 popular explanation. This restoration, so far as it has progressed, shows, 

 without reasonable doubt, that throughout Mesozoic time, and very 

 probably during a part of Tertiary time, the Carboniferous and Permian 

 strata of the Grand Canon district were horizontal and unbroken, the 

 greatest possible discrepancies being very small. Thus another and im- 

 portant point is gained, for it supports the conclusion that the configu- 

 ration of the Mesozoic sea-bottom, as well as its relations to the adjoin- 

 ing coasts, was, in the, middle and southern portions of the Grand Canon 

 district, favorable to the reception of the same mass of sediments as we 

 now find in the terraces of the High Plateaus. 



The argument from the drainage system is, in principle, the same as 

 that applied to the San Rafael Swell, though different in details. The 



