48 THE ATLANTIC. [ CHAP. I. 
It consists essentially of a brass cylinder, A (Fig. 10, I, I), 
which slides up and down a metal shank, B, of at least twice 
its length. When the water-bottle is sent down, the cylinder 
is fixed in the upper part of the shank, as in Fig. 10, I; and 
when it arrives at the bottom it is released and falls down to 
the lower part, as in II, where it rests on two accurately ground 
valves, C and D, which fit into two conical surfaces on the in- 
side of its upper and under edges. Thus the water which sur- 
rounds the shank at the moment of slipping is securely in- 
closed. The proper working of the instrument is dependent 
on the shank remaining straight ; any bend in it would cause 
the valves to leak. In the instrument used in the German 
expedition this was sufficiently well provided for, for shallow 
soundings with light weights, by the two valves being con- 
nected by a short iron rod, and the upper valve with the slip- 
ping arrangement by means of four slighter ones; but for deep 
soundings, where it is attached to a line along with a weight 
of three and often four hundred-weight, greater strength is nec- 
essary to enable it to withstand the knocks which, even with 
the greatest care, it is exposed to in being got over the ship’s 
side in a sea-way. Mr. Milne, of Edinburgh, into whose hands 
the construction of the instrument was put, has secured this 
end in a way which adds equally to the elegance and to the 
strength of the instrument. The shank and valves are one 
solid brass casting of the shape shown in the figure, the cylin- 
der is another, and the slipping arrangement, E, fixed to the 
end of a rod, F, of suitable length and great stoutness, is screw- 
ed into the top of the shank, the screw being secured by a 
rivet. The water inclosed is removed by means of a tap, G, 
passing through the lower valve, air being at the same time 
admitted at the top by the removal of a plug, H, from a hole 
in the upper valve. The lower valve and stop-cock are pro- 
tected from damage when striking against the ground by the 
casting extending about six inches below the valve. The ar- 
