652 
GEOLOGY: W. M. DAVIS 
points of the theory of subsidence;" he added that this "places the sup- 
porters of the theory of subsidence in a dilemna."^ At about the same 
time Hickson wrote: '^I am persuaded that .... the pres- 
ence of such an atoll as Passiac [in North Celebes] so close to a region 
of quite recent and considerable volcanic activity is difficult to account 
for under this [subsidence] theory. Murray went so far as to object 
to Darwin's theory of subsidence on the ground that even extinct vol- 
canoes are not likely to subside. He wrote: "Generally speaking, all 
the volcanic regions which we know have in the main been areas of ele- 
vation, and we would expect the same to hold good in those vast and 
permanent hollows of the earth which are occupied by the waters of the 
ocean Areas of local depression are to be looked for in 
the ocean basins on either side of and between groups of volcanic islands 
and atolls, and not on the very site of these islands. 
Much may be said against this obsolescent view, and in favor of the 
opposite view that volcanic action and subsidence may sometimes be 
closely associated. Strong testimony to this effect is offered by the re- 
peated occurrence of volcanic eruptions in areas of subsidence during 
the geological evolution of Great Britain, as worked out by an excep- 
tionally competent geologist whose conclusion is: "The study of the 
records of volcanic action in Britain proves beyond dispute that the vol- 
canoes of past time have been active in areas of the earth's surface that 
were sinking and not rising I do not wish to maintain 
that the downward movement was necessarily a consequence of volcanic 
ejections .... but I have sometimes asked myself whether it 
was not possibly increased as a sequel to vigorous action."^ An inter- 
esting piece of evidence concerning the subsidence of the great volcanic 
island of Hawaii during the later stages of its eruptive growth is furn- 
ished by Branner, who gives good reason for thinking that the deep 
canyons in the northeastern sector of the island have been eroded in 
part of an older, deeply dissected, and now partly submerged volcanic 
mass, the remainder of which has been overwhelmed and buried under 
the much more recent lava floods that cover the major area of the island.^ 
The newest discussion of this problem is by Molengraaf, who calls 
attention to the results of recent gravity determinations, from which it 
appears that the volcanic islands of the Pacific "as far as they have been 
studied are not isostatically compensated, and, without exception, show a 
larger or smaller positive anomaly of gravity These vol- 
canic islands, rising . . . as cones or groups of cones of consider- 
able bulk, cannot always remain in existence ; under the influence of gravity 
they will without exception yield and sink down slowly 
