20 Geological Effects of a Varying Rotation of the Earth, | January, 
think of the folds and faults of ancient strata. Thus far, we g 
have not considered the effect of the movement of the waters, 
transfer of sediment, etc. The latter would be of comparatively 
slight efficiency, as before stated. The former would be con- 
siderable, and might act as a counter check, and in this way 
produce slight vibrations, superimposed, as it were, on those of 
more importance, which we have just considered. 
These general movements of land and water need not conflict 
materially with the various local movements, which have been so 
clearly defined by various geologists. For example, the local 
folding of strata, and the elevation of mountains and continental 
plateaus; areas rising from local heating in the vicinity of vol- 
canoes, and, on the other hand, depressions resulting from the ac- 
cumulation of sediment. 
These, in all ages, must have been numerous. Over areas 
where both the general and the local influences were acting, of 
course the result would be the algebraic sum of the two. Per- 
haps further investigations may discover that certain so-called 
local movements are indirectly the result of the general influence 
supposed. For example, in the downward movement of either 
high or low latitudes, we have supposed that it was attended with 
and partially the result of, contraction of the earth. This would 
be likely to be attended with an elevation of mountain ranges. 
The elevations along the lines of volcanoes crossing the tropical 
regions at the present time may, perhaps, be considered examples 
of such action. Another point should be added before we attempt 
a practical application of our theory. The neutral belts, as they 
may be called, between the areas of apparent elevation and de- 
Í 
DE S NES 
seik 
pression, with respect to the sea-level, will be very variable. Some | 
reasons for the variability will be, (1) The different ellipticity of 
the earth, at different ages; (2) The amount of contraction of the 
earth in any vibration; (3) The different capacities of ocean beds- 
in different latitudes, pee the consequent varying rate of change 
` in the sea-level. This would affect especially the sea-level at the 
neutral belts. 
II. So much for the theory. Let us proceed to compare it 
with recorded facts. 
I. Changes during the present Epoch. 
The first attempt to map the areas of depression and elevation 
was made by Darwin, soon after his interesting observations O% 
