GEOLOGIC TIME. 321 



material, aud therefore the newer deposits were hiid down more rapidly.* 

 This does not impress me strongly; but from my experience among the 

 Paleozoic rocks I agree with Sir A. Goikie, that "we can see no i)roof 

 whatever, nor even any evidence which suggests — that on the whole the 

 rate of waste and sedimentation was more rapid during Mesozoic and 

 Paleozoic time than it is to-day."t 



Prof. Iluxley, in his presidential address to the Geological Society 

 of London in 1870, treats of the distribution of animals, and says of his 

 hypothesis that it " requires no supposition that the rate of change in 

 organic life has l)een either greater or less in ancient times than it is 

 now; nor any assumption, either physical or biological, which has not 

 its justification in analogous phenomena of existing nature.''^ 



In the Grand Canyon of the Colorado, Arizoua, there are 11,950 feet 

 of strata of Algonkian age extending uncomformably beneath the Cam- 

 brian. There is nothing m this section to indicate that the conditions 

 of deposition were unlike those of the strata of Paleozoic and Mesozoic 

 time. The sandstones, shakes, and limestones are identical in appear- 

 ance and characteristics with those of the latter epoch. The deposition 

 of sulphate of lime and gyi)sum occurred abundantly in the upper por- 

 tions of the series, and salt is collected by the Indians from the deposits 

 formed by the saline waters issuing from the sandstone 8,000 feet below 

 the sununit of the series. The sandstones and shales were deposited 

 in thin, even laminte and layers, and the sun cracks and ripple marks 

 give evidence of slow, uniform deposition. In the upper or Chuar ter- 

 raue, there are 235 feet of limestone. And in one of the layers of lime- 

 stone, 2,700 feet below the summit of the Chuar terrane, I find abun- 

 dant evidence of the presence of spicuhc of sponges and what appear to 

 be worn fragments of some small fossils. There is absolutely nothing 

 to indicate more rapid denudation and corresponding deposition in this 

 early pre-Canibrian series than we find in the Paleozoic, Mesozoic, or 

 Cenozoic fornmtions. 



PALEOZOIC SEDIMENTS OF THE CORDILLERAN SEA. 



The great sections of sedimentary. rocks in Arizona, Nevada, Utah, 

 Montana, and in Alberta, British America, all bear evidence that the 

 sediments of which they are built up were deposited in a connected and 

 continuous sea that extended from the vicinity of the thirty-fourth 

 parallel, on the south, to the Arctic Ocean on the north. Judging from 

 the data now available the width of this sea varies from 300 miles in 

 Nevada to 500 miles on the line of the fortieth parallel, and, with inter- 

 ruptions by mountain ridges, to 250 miles on the forty-ninth parallel. 

 It appears to have narrowed to the north in Alberta and British Colum- 



* GeoL England and JFalcs, 2d ed., 1887, p- 23. 

 \ Rept. Sixty-second Meethuj Brit. Assoc. Adi\ Sci., 1892, p. 19, 

 t Quart. Jour. Geol. Soc, 1870, vol. xxvi, p. Ixiii. 

 SM 93 21 



