It was but a few years ago that the idea was prevalent that the seas at
great depths were immense solitudes where life exhibited itself under no
form, and where an eternal night reigned. To-day, thanks to expeditions
undertaken for the purpose of exploring the abysses of the ocean, we
know that life manifests itself abundantly over the bottom, and that
at a depth of five and six thousand meters light is distributed by
innumerable phosphorescent animals. Different nations have endeavored to
rival each other in the effort to effect these important discoveries,
and several scientific missions have been sent to different points of
the globe by the English and American governments. The French likewise
have entered with enthusiasm upon this new line of research, and for
four consecutive years, thanks to the devoted aid of the ministry of the
marine, savants have been enabled to take passage in government vessels
that were especially arranged for making submarine explorations.
[Illustration: THE FRENCH SCIENTIFIC STEAMER TALISMAN.]
The first French exploration, which was an experimental trip, was made
in 1880 by the Travailleur in the Gulf of Gascogne. Its unhoped
for results had so great an importance that the following year the
government decided to continue its researches, and the Travailleur was
again put at the disposal of Mr. Alph. Milne Edwards and the commission
over which he presided. Mr. Edwards traversed the Gulf of Gascogne,
visited the coast of Portugal, crossed the Strait of Gibraltar, and
explored a great portion of the Mediterranean. In 1882 the same vessel
undertook a third mission to the Atlantic Ocean, and as far as to the
Canary Islands. The Travailleur, however, being a side-wheel advice-boat
designed for doing service at the port of Rochefort, presented none
of those qualities that are requisite for performing voyages that are
necessarily of long duration. The quantity of coal that could be stored
away in her bunkers was consumed in a week, and, after that, she could
not sail far from the points where it was possible for her to coal up
again. So after her return Mr. Edwards made a request for a ship that
was larger, a good sailer, and that was capable of carrying with it a
sufficient supply of fuel for remaining a long time at sea, and that
was adapted to submarine researches. The Commission indorsed this
application, and the Minister of Instruction received it and transmitted
it to Admiral Jauréguiberry--the Minister of the Marine--who at once
gave orders that the Talisman should be fitted up and put in commission
for the new dredging expedition. This vessel, under command of Captain
Parfait, who the preceding year had occupied the same position on the
Travailleur, left the port of Rochefort on the 1st of June, 1883, having
on board Mr. Milne Edwards and the scientific commission that had been
appointed by the Minister of Public Instruction. The Talisman explored
the coasts of Portugal and Morocco, visited the Canary and Cape Verd
Islands, traversed the Sea of Sargasso, and, after a stay of some time
at the Azores, returned to France, after exploring on its way the Gulf
of Gascogne (Fig.).
[Illustration: FIG.1.--CHART OF THE TALISMAN'S VOYAGE.]
The magnificent collections in natural history that were collected
on this cruise, and during those of preceding years made by the
Travailleur, are, in a few days, to be exhibited at the Museum of
Natural History. We think we shall be doing a service to the readers of
this journal, in giving them some details as to the organization of the
Talisman expedition as well as to the manner in which the dredgings were
performed.
[Illustration: FIG.2.--PLAN OF THE VESSEL.]
The vessel, as shown by her plan in Fig. 2, had to undergo important
alterations for the cruise that she was to undertake. Her deck was
almost completely freed from artillery, since this would have encumbered
her too much. Immediately behind the bridge, in the center of the
vessel, there were placed two windlasses, one, A, to the right, and the
other, B, to the left (Fig. 2). These machines, whose mode of operation
will be explained further along, were to serve for raising and lowering
the fishing apparatus. A little further back there were constructed
two cabins, G and HH. The first of these was designed to serve as a
laboratory, and the second was arranged as quarters for the members of
the mission.
The sounding apparatus, the Brothergood engine for actuating it, and the
electric light apparatus were placed upon the bridge. The operating
of the sounding line and of the electric light was therefore entirely
independent of that of the dredges. On the foremast, at a height of
about two meters, there was placed a crane, F, which was capable of
moving according to a horizontal plane. Its apex, as may be seen from
the plan of the boat, was capable of projecting beyond the sides of the
ship, to the left and right. To this apex was fixed a pulley over which
ran the cable that supported the dredges or bag-nets, which latter were
thus carried over the boat's sides.
[Illustration: FIG.3.--DIAGRAM OF THE THIBAUDIER SOUNDING APPARATUS.]
The preliminary operation in every submarine exploration consists in
exactly determining the depth of the sea immediately beneath the vessel.
To effect this object different sounding apparatus have been proposed.
As the trials that were made of these had shown that each of them
possessed quite grave defects, Mr. Thibaudier, an engineer of the navy,
installed on board the Talisman last year a new sounding apparatus which
had been constructed according to directions of his and which have given
results that are marvelous. The apparatus automatically registers the
number of meters of wire that is paid out, and as soon as the sounding
lead touches bottom, it at once stops of itself. This apparatus is shown
in Fig. 4, and a diagram of it is given in Fig. 3, so that its operation
may be better understood. The Thibaudier sounding apparatus consists of
a pulley, P (Fig. 3), over which is wound 10,000 meters of steel wire
one millimeter in diameter. From this pulley, the wire runs over a
pulley, B, exactly one meter in circumference; from thence it runs to a
carriage, A, which is movable along wooden shears, runs up over a fixed
pulley, K, and reaches the sounding lead, S, after traversing a guide,
g, where there is a small sheave upon which it can bear, whatever be the
inclination of the boat. The wheel, B, carries upon its axle an endless
screw that sets in motion two toothed wheels that indicate the number
of revolutions that it is making. One of these marks the units and the
other the hundredths (Fig. 5). This last is graduated up to 10,000
meters. As every revolution of the wheel, B, corresponds to one meter,
the number indicated by the counter represents the depth. Upon the axle
of the winding pulley there is a break pulley, p. The brake, f, is
maneuvered by a lever, L, at whose extremity there is a cord, C, which
is made fast to the carriage, A. When, during the motions due to
rolling, the tension of the steel wire that supports the lead diminishes
or increases, the carriage slightly rises or falls, and, during these
motions, acts more or less upon the brake and consequently regulates the
velocity with which the wire unwinds. When the lead touches bottom, the
wire, being suddenly relieved from all weight (which is sometimes as
much as 70 kilos), instantly stops.
[Illustration: FIG. 4.--GENERAL VIEW OF THE SOUNDING APPARATUS IN THE
"TALISMAN:"]
The maneuver of this apparatus may be readily understood. The apparatus
and its weights are arranged in the interior of the vessel. A man bears
upon the lever, L (Fig. 3), and the counter is set at zero. All being
thus arranged, the man lets go of the break, and the unwinding then
proceeds until the lead has touched bottom. During the operation of
sounding, the boat is kept immovable by means of its engine, so that the
wire shall remain as vertical as possible. The bottom being reached, the
unwinding suddenly ceases, and there is nothing further to do but read
the indication given by the differential counter, this giving the depth.
[Illustration: FIG. 5.--APPARATUS FOR MEASURING THE LENGTH OF THE WIRE
PAID OUT.]
Near the winding pulley, there is a small auxiliary engine, M, which
is then geared with the axle of the said pulley, and which raises the
sounding apparatus that has been freed from its weight by a method that
will be described further along.
We have endeavored in Fig. 4 to show the aspect of the bridge at the
moment when a sounding was about being made. From this engraving (made
from a photograph) our readers may obtain a clear idea of the Thibaudier
sounding apparatus, and understand how the wheel over which the wire
runs is set in motion by the Brothergood engine.--_La Nature_.
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