Dr. C. Ricketts—Oscillation of the EKarth’s Crust. 300 
for the accumulations which so constantly accompany it, nor is it 
conceivable that the continuance of the same agency would occasion 
its re-elevation. If in any case depression has been due to such in- 
fluence, it may be looked for in the extreme depths of the ocean, 
where the constant temperature nearly approaches the freezing-point ; 
certainly not in the Arctic regions, where the mean annual temperature 
is very much lower; for though Greenland is sinking, Norway and 
Spitzbergen are rising; so also are extensive districts near to or 
within the Arctic cirele—Labrador, Hudson’s Bay, the Arctic Archi- 
pelago and the shores of Behring’s Straits '—affording unmistakable 
testimony to elevation of the land within a recent period; in some 
cases affording evidence that such is now in progress. It has 
recently been estimated that the shores of Hudson’s Bay have risen 
in places from five to ten feet within the century.’ 
Near the mouths of large rivers, in deltas and in bays, and during 
former geological periods, where strata have been deposited, depression 
has been persistent, even though such a thick covering has been 
overlaid as would retain the central heat and exclude the external 
cold. 
Deposition and subsidence having been constant and contempo- 
raneous during all geological periods, the phenomena can only be 
attributed to and associated together as cause and effect. Whether 
it be strata laid down in the sea, those forming deltas near the 
mouths of large rivers, or a thick covering of snow that has fallen 
on the land, the accumulated weight presses down the crust of the 
earth. 
It is also nearly as certain that elevation of continents is to be 
attributed to denudation to which the land has been subjected, 
causing a relief of pressure, whether by the disintegration of the 
rocky mass or by dissolution of glaciers ; in the former case it might 
be further assisted by the transfer of the molten substratum as 
a consequence of depression in another area. 
In an address delivered at Sheffield more than three years ago, 
having reference to the Coal formation, it was remarked that “ the 
more the subject is considered, the more astonishing does it become 
for the regularity of the subsidence; and its amount must have kept 
pace with the thickness of the accumulating deposits ;” * but these 
concurrent phenomena demand more than wonder, they require 
serious and careful attention such as is yet to be bestowed upon 
them. This is the more necessary, as in them may be found the 
great motive power which not only produces changes of level 
in the earth’s crust, but also permits and induces many other 
alterations in its physical condition. 
Mr. H. B. Woodward, F.G.S., quite recently, in the Transactions 
1 Recent Elevation of the Earth’s Surface in the Northern Circumpolar Region, 
by Henry H. Howorth, Arctic Manual, 1875, Reprinted from the Journal of the 
Royal Geographical Society, vol. xl. 1873. 
* The Times, Jan. 14, 1880. 
3 President’s Address to Section C, at Sheffield, by Professor P. Martin Duncan, 
F.R.S., British Association Report, 1879, p. 330. 
