EQUIPMENT. 11 
and on striking bottom the bail is prevented from getting over 
the top of the detacher by the bearing which the sinker has 
against the under part of the cone. 
When the sinker strikes bottom the slacking of the sounding- 
line or wire trips the tumbler, and the sinker is free to slide off 
the cylinder. This tumbler is kept back by the spring JV, and 
the bail cannot be rehooked when the line is hauled taut to reel 
in. The resistance of the bottom soil raises the poppet-valve Z^, 
and the specimen of the bottom enters the cylinder, the water 
within the cylinder being free to escape through the various 
perforations P, P, etc. On hauling back the poppét-valve falls, 
or is forced by its spring, 77, to the valve-seat, and the cone 7 
falls, closing the water apertures. When the rod has been got 
on deck the lower part of the cylinder is unscrewed, when the 
specimen of soil may be extracted. To prevent the wire from 
coiling on the bottom, a piece of rope somewhat less than quar- 
ter of an inch in diameter, and from nine to twelve fathoms long 
(the stray line), is spliced to the wire, and to this is attached the 
sinker, detacher, and any instrument sent down while making : 
sounding. 
The great advantage of sounding with wire is in the very 
great strength of the wire as compared wi;h that of stout cod- 
line; also in the smoothness of its surface, by which the friction 
is reduced to a minimum; so that a wire weighing, say, twelve 
pounds in water to the mile, can readily take down a hundred- 
pound shot, and not only bring up the fourteen pounds weight 
of the sinker and collecting cylinder, but carry besides the 
thermometers needed to ascertain the temperature both of the 
bottom, and of intermediate depths as well. It would, however, 
in practice be more convenient to use a separate reel, and wire 
slightly heavier for making the temperature observations, and 
for having the water-cups attached. 
The weight of the wire payed out in the deepest soundings yet 
made, 4,65 b fathoms, will, in water, be less than sixty pounds, so 
that the weight of the TEN (one hundred pounds or more) ean 
always be made to exceed that of the wire, an impossibility in 
the case of soundings made with hemp-lines. So far as accuracy 
is concerned, everything also is in favor of the wire method. 
The time of striking bottom is determined, not as in the case of 
