:'».")ii The American Geologist. December, 1893 
the sedimentary rocks the land surface consisted of crystalline or igne- 
ous rocks subject to rapid decomposition owing to the composition of 
the atmosphere and to their inherent tendency to decay. They must 
have yielded to wear and removal with a facility unknown amongst me- 
chanically-formed and detrital strata where erosion operates. He thus 
accounts for one of the factors that gave the large dimensions and 
thicknesses of the earlier formations. Mr. Wallace thinks that geolog- 
ical change was probably greater in very remote times,* stating that 
all telluric action increases as we go back into the past time and that 
all the forces that have brought about geological phenomena were 
greater.")" 
Dr. Woodward says on the opposite view, that in the earliest geolog- 
ical periods each bed of sand, clay, limestone, etc., had actually to be 
formed, and that later deposits had the older sedimentary ones to fur- 
nish material, and, therefore, the newer deposits were laid down more 
rapidly.J This does not impress me strongly; but from my experience 
among the Paleozoic rocks I agree with Sir A. Geikie, that "we can see 
no proof whatever, nor even any evidence which suggests that on the 
whole the rate of waste and sedimentation was more rapid during Mes- 
ozoic and Paleozoic time than it is to-day. ''§ 
Prof. Huxley, 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 been 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 Ganyon of the Colorado, Arizona, there are 11,950 feet 
of strata of .Algonkian age extending unconformably beneath the 
Cambrian. There is nothing in this section to indicate that the condi- 
tions of deposition were unlike those of the strata of Paleozoic and 
Mesozoic time. The sandstones, shales, and limestones are identical 
in appearance and characteristics with those of the latter epoch. The 
deposition of sulphate of lime and gypsum occurred abundantly in the 
upper portions 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 summit of the series. The sandstones and shales 
were deposited in thin, even lamina? and layers, and the sun cracks and 
ripple marks give evidence of slow, uniform deposition. In the upper 
or Chuar terrane, there are 235 feet of limestone. And in one of the 
layers of limestone, 2,700 feet below the summit of the Chuar terrane, 
*Island Life, 2d Ed., 1892, pp. 228-224. 
tSir William Thompson (Lord Kelvin) inferred from his investigations upon the 
cooling of the earth, that the general climate cannot be sensibly affected by conducted 
heat at any time more than 10,000 years after the commencement of superficial solidi- 
fication. Treatise on Natural Philosophy, Cambridge, 1888, vol. i, pt. 2. p. 478. 
Of the degree of the sun's heat we know so little that conjectures in relation to it 
have little force against the conditions indicated by the sedimentary rocks and their 
contained organic remains. 
IGeol. England and Wales, 2d Ed., 1887, p. 23. 
SKept. Sixty-second MeetiDg Hrit. Assoc. Adv. Sci., 1892, p. lit. 
'Quart. Jour. Geol. Soc, vol. 26, 1870, p. lxiii. 
