MR. HOPKINS’S RESEARCHES IN PHYSICAL GEOLOGY. 
53 
will be impossible for the mass to subside, when the elevatory force shall cease, into 
that position which it originally occupied. It will be formed into an arch capable 
(if its abutments be sufficiently strong) of entirely or partially supporting itself. Con- 
sequently, if the cause producing the intumescence of the fluid mass cease to act, 
and that mass return nearly to its original dimensions, the pressure of the superin- 
cumbent solid mass may, in the manner now described, be entirely or partially re- 
moved from the fluid. Hence, assuming that solidification is promoted by great 
pressure, it evidently appears how a portion of the interior mass might be maintained 
in a state of fluidity by the removal of a superincumbent pressure, which would other- 
wise have brought it to a state of solidity. 
It is not here essential to suppose that the arch shall entirely support itself. It 
may be partly supported by the fluid beneath, or it may break down in certain points, 
or along certain lines, and form there new supports, intermediate to the extreme ones. 
Instead of one continuous internal lake, a number may thus be formed, connected 
with each other by more or less obstructed channels of communication, as I have 
supposed in the exposition of my theoretical views on the Elevation of the Wealden 
District, recently laid before the Geological Society. It is the existence of subterra- 
nean lakes under this form, which best enables us, as I conceive, to account for the 
observed phenomena of elevation. 
10. The above view of the relative displacements of the different portions of an 
uplifted and disrupted solid mass, as resulting from its geological elevation, is strongly 
confirmed by its enabling us to account so completely for the law, first recognized by 
Mr. Phillips, and which I have myself verified in numerous instances, in the relative 
displacement of the beds on opposite sides of a fault. In diagram (2.) we observe 
that the line/ 7 g' is relatively depressed below e f, with which it was originally con- 
tinuous ; i. e. the beds are lowest on that side of the fault towards which the plane of 
the fault inclines from the vertical in descending. This precisely accords with the 
law above alluded to. It will be observed to hold at each of the faults represented 
in the diagram, and probably admits of fewer exceptions than almost any other law 
observable in the phenomena of elevation. 
§. Permanence in the Inclination of the Earth's Axis. 
11. To the conclusions above deduced from the investigations of my two preceding 
memoirs, I may add that of the permanence in the mean inclination of the earth’s 
axis to the plane of the ecliptic. This permanence has been frequently insisted on, 
and is highly important with reference to our speculations on the causes of those 
changes of superficial temperature which certain geological phenomena seem so un- 
equivocally to indicate. The proof, however, which has hitherto been given of this 
constancy of inclination has rested on the hypothesis of the entire solidity of the globe, 
an assumption which, whatever may be the actual state of our planet, can never be 
admitted as necessarily applicable to it at all past epochs of time, at which organic 
