3802 Dr. C. Ricketts—Oscillation of the Earth's Crust. 
have not each taken precisely the same view of the process by which 
the result ensues; but whatever the precise process may be, the 
chemical theory, if true, removes the objection made by Croll 
to Heckel’s contention as to the immensity of time, which the 
phenomena of Evolution show must have elapsed since the dawn 
of life upon the earth. 
TV.—On AccumMULATION AND DENUDATION, AND THEIR INFLUENCE IN 
CausInc OSCILLATION OF THE Hartu’s Crust. 
By Cuarzets Ricxerts, M.D., F.G.S. 
O fact in Physical Geology is more frequently recorded than a 
simultaneous occurrence of subsidence of the earth’s crust 
where deposition of sedimentary strata has been in progress. 
Reference is often made to the fact that the basement beds of 
different sedimentary formations were deposited in shallow water, 
and to the indications presented by subsequent deposits that they 
were accumulated in a sea of moderate depth. On them immense 
accumulations may have been deposited in successive strata, amount- 
ing even to miles in thickness; showing that with the deposition 
there has been a corresponding depression of the original surface. 
Though these phenomena are so inseparable in their occurrence and 
so well known, English geologists, until the last few months, have 
made little, it may even be said no endeavour, to determine whether 
they should be associated as cause and effect. This has not been the 
case with American geologists. 
In 1859 Professor James Hall of the United States determined 
that “the removal of large quantities of sediment from one part of 
the earth’s crust, and its transportation and deposition in another, 
would produce oscillation of level. When these are spread along a 
belt of sea-bottom, the first effect of this great augmentation of 
matter would be to produce a yielding of the earth’s crust beneath, 
and a gradual subsidence would be the consequence.” He founded 
this opinion on the results of an examination of Paleozoic strata 
along the Appalachian chain, of which strata the Carboniferous 
formation alone reaches to a thickness of 14,000 feet. It is evident 
“that the depth of the sea was not originally so great as the thick- 
ness of these accumulations, and the occurrence of ripple marks, 
marine plants, and other conditions prove that the sea in which 
these deposits were made was at all times shallow or of moderate 
depth.” ? 
In North America it is so generally accepted that the phenomena 
1 The following are Croll’s words: ‘‘ Prof. Heckel may make any assumption he 
chooses about the age of the sun, but he must not do so in regard to the sun’s heat. 
One who believes it inconceivable that matter can be created or annihilated may be 
allowed to maintain that the sun existed from all eternity, but he cannot be permitted 
to assume that our luminary has been losing heat from all eternity.’’—‘‘ Nature”’ 
for Jan. 10, 1878. 
* Paleontology of New York, vol. iii., Introduction. An account of Professor 
Hall’s opinions is given in Chemical and Geological Essays, Essay V., by T. 
Sterry Hunt, LL.D., F.R.S. 
