APRIL 18, 1884.] 
while the thrown side went down, the opposite 
side went up. To explain the first hypothesis, 
we must have either a condensation of the mass 
underlying the thrown side, extending toward 
the centre of the earth, or a transferrence of 
the material from immediately beneath the 
thrown side to some other part of the interior 
of the earth. A condensation or a transfer- 
rence is absolutely necessary. The latter hy- 
pothesis is the hypothesis of a fluid interior. 
In the second case mentioned above, where 
the side opposite the thrown block is supposed 
to be upheaved, there must be either an ex- 
pansion of the immediately underlying material, 
or a transferrence of material. The hypothe- 
sis of a vacuum beneath is untenable, for it 
can be easily demonstrated that the strength 
of materials could not possibly sustain the re- 
sultant stress. We are forced, therefore, to 
the conclusion that there is either an expan- 
sion or a transferrence of material, the latter 
being equivalent to the hypothesis of an in- 
terior fluid. The third case is, that one side 
went down while the other side went up; and 
this hypothesis is sustained by many concomi- 
tant facts. In this case there must either be 
a condensation on one side and an expansion 
on the other, or a transferrence of material: 
and geologists conclude that there has been a 
transferrence of material; i.e., they postulate 
a fluid interior. 
Faults like the one above mentioned are not 
infrequent. Many are discovered of greater 
magnitude, many more of less; and, wherever 
the geology of any great district of country 
has been explored, such faults have been dis- 
covered, so that they are now known to exist 
in great numbers throughout all the studied 
portion of the land-surface of the earth. Every 
year’s research —it may almost be said every 
month’s or every week’s research — adds _ to 
the number. 
In addition to these faults, geologists are 
everywhere discovering flexures, many of them 
simple monoclinal bendings by which the crust 
of the earth is displaced; one side being low- 
ered, or the other raised, or the two simultane- 
ously moved. Again: great anticlinal flexures 
are discovered, sometimes developed to ap- 
pressed folds, and monoclinal and anticlinal 
flexures are found throughout the whole known 
portion of the land-surface of the earth; so 
that these displacements by faulting and by 
flexure are widely and generally distributed. 
Again: displacement is a phenomenon, not 
simply of the present time, but of all known 
geologic time; as like displacements are dis- 
covered of various ages, beginning with the 
SCIENCE. 
481 
oldest archaean, and extending to the present 
time. Nor can we say that displacement was 
either greater or less in earlier geologic times 
than in the present. Such displacements as 
have been here briefly characterized have oc- 
curred again and again in the same district of 
country, sometimes following the old lines, 
oftener along new lines, traversing in diverse 
ways the same territory; so that blocks of 
the crust that have at one time been upheaved 
have at another time subsided, and blocks that 
at one time have subsided have at another 
been upheaved. It is sometimes possible 
to discover as many as six or more epochs 
of alternating displacement; in the first the 
rocks going up, in the second down, then 
up, then down, ete. The evidence of re- 
peated displacement in the same district is 
not simply local, but is widely spread through- 
out the known portion of the land-surface of 
the earth. 
But the evidence for a fluid condition of the 
interior, derived from displacement, does not 
end here. Take first a simple example lke 
the following: a block of stony crust is sepa- 
rated from the adjacent rock on all sides by 
fracture. Such a block may be many miles in 
length (ten or a hundred), and of varying width 
(two or twenty miles). Such a severed block 
will be found by the geologist to have careened, 
one side or edge going down while the other 
came up. In order to explain this displace- 
ment, it is necessary to assume that there was 
an increasing rate of expansion beneath the 
block from the axis of rotation to the upturned 
edge, and an increasing condensation of the 
underlying material from the same axis to the 
edge of the down-thrown side, or to assume 
that it careened on a fluid mass. The latter 
is the explanation accepted by geologists. 
Again: such a block may be broken into many 
parts, each one of which behaves as an inte- 
ger, and careens on its own axis. Many such 
careened blocks have been discovered, though 
this particular form of displacement has not 
been described by geologists to the extent of 
those mentioned above. 
II. The argument from vulcanism. 
Fluid matter comes up from unknown depths, 
and is sometimes intercalated between horizon- 
tal or dipping beds of sedimentary rock; but 
oftener it comes to the surface and is poured 
out in sheets, sheet being piled on sheet until 
mountains and mountain systems are pro- 
duced. The amount of matter thus brought 
up from below is great; and it occupies large 
