. , í f e 1
I’!
burning equally well; a bituminous oil; a substance like coal-
tar ; and a residuum, similar to coke; result from its distillation.
Electricity may have been a powerful agent in crystallization
; in the rapid deposition of strata ;* in the formation of
mineral veins;# in earthquakes and volcanoes ; in the formation
or decomposition of water; and in other ways of which we
are yet, and perhaps ever shall be, totally ignorant.
Successive strata may have been rapidly deposited by tidal
oscillations and currents, aiding chemical or mechanical combinations.
The depth to which bodies would sink in an ocean several
miles deep has not been proved, and tliere is reason to think
that it is much less than people generally imagine. An eminent
man has said that a knowledge of “ the depression of the bed
of the ocean below the surface, over all its extent, is attainable
(with whatever difficulty and however slowly) by direct sounding
;”] and, in consequence of a conversation on this subject
with him in 1836, he wrote to me, suggesting a mode which
might he tried. I consulted with a friend as to the possibility
of success, and his letter,^ taken in connection' with the facts
• Crosse. t Fox.
X Treatise on Astronomy, by Sir Jobn Herschel—Cabinet Cyclopaedia—
page 154. .
§ “ I return Sir John JlerscheTs letter on deep-sea sounding. Anything
from him is sure to be interesting and instructive; but there is a
circumstance unnoticed in his communication which might obstruct the
descent of a sounding apparatus to very great depth.
“ Mr. Perkins found that at a depth of only 3,000 feet, sea-water was
compressed l-27th of its bulk at the surface. (LibL of Useful Knowledge,
vol. 1. Art. Hydrostatics.) Hydrostatic pressure has usually been estimated
from depth alone, assuming that the density of the fluid was uniform
; such, however, cannot be the case in an elastic fluid like water,
for at great depths, being in a compressed state, it is more dense than at
the surface.
“ In estimating the amount of hydrostatic pressure at great depths, we
should know the vertical height of the column and mean density of the
fluid ; and since density increases with depth, by reason of superincumbent
pressure, the water at great depths must be enormously ccinpressed,
and,
il aH
1 elated hy Scoresby ;* with what has been found by those who
have sounded to great depths; and with my own practical experience
in sounding—has induced me to think that man never
will reach the lowest depths of the deepest oceans hy any method
his ingenuity may contrive;—because the water increases in
density with the depth, in a ratio perhaps more than arithmetical.
Every seaman knows that in sounding at great depths
very heavy leads must be used with ordinary lines, or very
thin lines with ordinary leads ; the object being the same—that
of overcoming the augmenting buoyancy of the line by a weight
unusually heavy. But line, such as is used for sounding, is
not buoyant at the surface of the sea ; a coil of it thrown overboard
sinks directly. Then what is it that causes any weight
attached to a sounding-line to sink slower and more slowly,
and, consequently, in a very dense state. Let us now inquire howincreasing
density (from compression alone) might affect an apparatus sent down
by a weight, in order to reach the bottom, presuming that the solids
composing the float and sinker were incompressible, and retained their
form and magnitude during the operation.
“ Letbees’-wax be a float, and cast-iron a sinker, and let each,for illustration,
be one cubic foot in dimensions. Let it be possible that at some
depth water may be compressed into one-fourth of its bulk at the surface,
and still retain the properties of a fluid ; let it also be granted that a’
solid will swim if speciflcally lighter than the contiguous fluid, and sink
if heavier than an equal volume of the fluid. The specific gravity of
bees’-wax is stated to be 964; that of cast iron, 7248; and that of seawater
at the surface, 1028 : hence the buoyancy*of wax immersed in seawater
at the surface, may be called 64, and the tendency of cast-iron to
sink, from the same surface, 6220. Deducting 64, we have 6156 as the
whole tendency of the mass (wax attached to iron) to sink from the surface.
Let us now suppose that the machine has attained a depth where
the water is compressed into a four-fold density, represented by 4112 for
a cubic foot; and we have 3148 for the tendency of the wax to float, but
only 3136 for tbe tendency of the iron to sink : and the inclination to
ascend rather than descend, might be represented by 12. Thus we see
that an apparatus may not be certain of arriving at the bottom of an
ocean : as in an opposite manner, a balloon may not reach the highest
regions of the atmosphere. Either machine could only attain a position
where there would be no tendency either to descend or ascend.
Plymouth, 24th Feb. 1837. , “ I F i l i .i a m W a i .k e r . ”
• Scorosby’s Arctic Reg]ions.