106 
ELEMENTS OF GEOLOGY. 
sweep it away as readily as it does every temporary shoal 
that accumulates from time to time around a sunk vessel on 
the same hank."^ 
No observed geographical changes in historical times en¬ 
title us to assume that where upheaval may be in progress 
it proceeds at a rapid rate. Three or four feet rather than 
as many yards in a century may probably be as much as 
we can reckon upon in our speculations; and if such be the 
case, the continuance of the upward movement might easily 
be counteracted by the denuding force of such currents aid¬ 
ed by such waves as, during a gale, are known to prevail in 
the German Ocean. What parts of the bed of the ocean are 
stationary at present, and what areas may be rising or sink¬ 
ing, is a matter of which we are very ignorant, as the tak¬ 
ing of accurate soundings is but of recent date. 
Newfoundland Bank .—The great bank of Newfoundland 
may be compared in size to the whole of England. This 
part of the bottom of the Atlantic is surrounded on three 
sides by a rapidly deepening ocean, the bank itself being 
from twenty to fifty fathoms (or from 120 to 300 feet) un¬ 
der water. We are unable to determine by the comparison 
of difierent charts made at distant periods, whether it is un¬ 
dergoing any change of level, but if it be gradually rising 
we can not anticipate on that account that it will become 
land, because the breakers in an open sea would exercise a 
prodigious force even on solid rock brought up to within a 
few yards of the surface. We know, for example, that when 
a new volcanic island rose in the Mediterranean in 1831, the 
waves were capable in a few years of reducing it to a sunken 
rock. 
In the same way currents which flow over the Newfound¬ 
land bank a great part of the year at the rate of two miles 
an hour, and are known to retain a considerable velocity 
to near the bottom, may carry away all loose sand and mud, 
and make the emergence of the shoal impossible, in spite of 
the accessions of mud, sand, and boulders derived occasion¬ 
ally from melting icebergs which, coming from the northern 
glaciers, are frequently stranded on various parts of the 
bank. They must often leave at the bottom large erratic 
blocks which the marine currents may be incapable of mov¬ 
ing, but the same rocky fragments may be made to sink by 
the undermining of beds consisting of finer matter on which 
the blocks and gravel repose. In this way gravel and 
boulders may continue to overspread a submarine bottom 
after the latter has been lowered for hundreds of feet, the 
* Principles, lOth ed.,vol. i., p. 569. 
