450 
at the upper end of which is'a ring, and to this is 
attached the sounding-line. When this is pulled, 
the rod moves up slightly, a stop controlling its 
course at a certain point. On the opposite sides 
of this rod are hooks. To accelerate the descent 
of the sounder, it is loaded with large cast-iron 
disks. On the out- 
er surface: of these 
disks are two longi- — 
tudinal grooves 
through which pass 
wires from a ring 
under the _ lowest 
SCIENCE. 
disk, ending in two 
rings resting on 
hooks just below the 
upper end ‘‘of* the 
sounding-rod. 
When the lead 
reaches the bottom, 
and the pull on the 
sounding-wire ceas- 
es, the rod to which 
the wire is attached falls 
-in the upper compart- 
ment of the sounding- 
tube, releasing the rings 
from the hooks, and al- 
lowing the iron disks to 
slide off. Relieved of 
the extra weight, the 
lead is easily raised. 
The lower end of the 
tube is supplied with 
valves, which are closed 
by the falling of the iron 
disks, and enclose any 
loose matter on the bot- 
tom, the action being 
assisted by a coating of 
tallow. 
The thermometers 
in the tube falls to the lower end, which is gradu- 
meds : eee ici 
On the Travailleur a hemp rope was used for the 
Fie. 6.— Windlass for raising the dredges and trawls. 
dredges, of which we give a cut showing its actual 
size (fig. 8, no. 1), which was not only cumbersome, 
but had little strength, breaking under a load heavier 
than two thousand kilograms. On the Talisman a 
wire rope (fig. 8, no. 2) was employed, composed of 
six strands of seven steel wires each, twisted around 
a hempen core. Notwithstanding that it was formed 
of forty-two wires, its diameter was only one centi- 
metre. Upon trial it bore a weight of forty-five hun- 
dred kilograms without breaking. 
The collecting-apparatus used on board the Talis- 
man consisted of dredges and trawls. The dredges 
have an iron frame of rectangular shape, to which is 
fitted a sack formed of closely-woven cords. The 
sides of the frame, before reaching the bottom, stand 
up at right angles, and are provided with scrapers 
cut and inserted at such an angle that they not only 
used to determine 
the temperature of 
the water at great 
depths often have 
to sustain a press- 
ure greater than 
three hundred at- 
mospheres; that is, 
more than _ thirty 
tons to a _ square 
decimetie. Twoare 
used, incased in very 
thick glass walls. 
When the lead 
reaches the bottom, and the extra weights be- 
come detached, the catch holding the thermome- 
ter-case is released by the breaking of the cord 
attached to the long lever shown in the upper 
part of fig. 5, and the thermometers are inverted. 
The mercury-column is then broken at a point aboye 
the bulb where the tube is narrow, and the mercury 
Fie. 5.— Sounding-cup and ther- 
mometer. 
Fig. 7. — Reel for wire rope. 
detach clinging objects, but gather the very smallest 
specimens on the bottom. In speaking of the dredge 
of Dr. Ball, which for more than ten years (1838-48) 
[Vou IIL, N 0:62; 
