DIASTROPHISM AS BASIS OF CORRELATION 689 
the sea. They are all surrounded by a border-belt, overflowed by 
the sea to the nearly uniform depth of 100 fathoms. ‘These submerged 
tracts are all crossed by channels, implying a recent emergent state. 
None of the continents is covered widely by recent marine deposits, 
and yet all show some measure of these. Wide recent transgressions 
in one part do not stand in contrast with great elevations in another. 
Even beyond what theory might lead us to expect, when we duly 
recognize the warpings incidental to all adjustments, the recent rela- 
tions of the continents to the seas conform to one type. ‘The 
10,000,000 square miles of continental margin, now submerged, is 
distributed around the borders of all the continents with a fair degree 
of equability. May we not, therefore, agree that in the world-wide 
phases of diastrophic movements, the basins have been additionally 
depressed and the continents repeatedly rejuvenated. 
It is important that we should agree, or agree to disagree, on one 
further point. Have diastrophic movements been in progress con- 
stantly, or at intervals only, with quiescent periods between? Are 
they perpetual or periodic? ‘The latter view prevails, I think, among 
American geologists. This view has acquired especial claims since 
base-leveling has come to play so large a part in our science, for it is 
clear that the doctrine of base-leveling is specifically inconsistent 
with the doctrine of perpetual deformation, for the very conditions 
prerequisite to the accomplishment of base-leveling involve a high 
degree of stability through a long period. The great base-levelings, 
and the great sea-transgressions, which I think are little more than 
alternative expressions for the same thing, have, as their fundamental 
assumption, a sufficient stability of the surface to permit base-leveling 
to accomplish its ends. Shall we not therefore agree that there has 
been periodicity in the world-warping deformations? Let this not 
be held with such exclusiveness that we fail to recognize duly the 
effects of the adjustment of minor stresses, at other times. ‘These 
may be preliminary or after-effects of the larger movements, or they 
may be due to local-stresses more or less independent of the general 
body-stresses. These quite certainly have been present, and have 
produced intercurrent departures from the strict tenor of the great 
systematic movements. 
If there is need for additional argument on periodicity, it may be 
