DEEP-SEA EXPLORATION. 
369 
the sinker h. The dredge rope is shackled to the ui)per link and serves as a tow 
liTie. The lower bridle c has two legs, each 10 feet in length, of 2-inch manila rope, 
the free ends seized to opposite sides of the ring and a 00 pound sounding shot toggled 
to the lower end as a sinker to insure the apparatus going down vertically. The net 
n is cylindrical in form, 5i feet long, the lower half lined with mosipiito net and 
the lower third with an additional lining of silk bolting-cloth. The tail lashing p 
having been adjusted, one end is carried down and made fast to tlie lower bridle at d 
to keep the net in place while it is being lowered. 
Four small brass riiuis are stitched to the net at equal intervals, a few inches 
below the upper edge of the silk lining, through which is rove a drawstring of braided 
.signal halyard stuff, or soft white cod line, which makes a round turn, the ends being 
finally jiassed in opposite directions through the same ring, rove through blocks on 
the bridle legs and bent to the weights g, which weigh 14 pounds each. Two tripping 
lines m, of cod line, with eyes in their upper ends, are hooked over the tumbler j of the 
friction clamp t; the other ends are passed down through leads on the ring a and bridle 
legs c, and bent to the weights r/, suspending them at the height of the drawstring- 
blocks, allowing the drawstring to hang loosely about the net and the latter to retain 
its natural form while going down and until it is closed by the action of the messenger. 
To use the net, prepare it as in tig. 1, lower it vertically, from 20 to 25 fathoms 
per minute, until it reaches the desired depth, and tow it from to 2 knots per hour, 
heaving in, veering and varying the speed, in order to maintain it at the projier depth, 
which can be determined within a few fathoms by observing the angle of the towline 
with the dredging quadrant. 
To recover the net, stop and back until the towline is vertical, heaving in during 
the operation in order to maintain the net at the same depth at which it had been 
towed; then send the messenger down to act on tumbler of friction clamp, release 
tripping lines, and close lower part of net (fig. 6). The messenger is in two parts, 
which are held on the towline by seizings of marline. It sinks from 100 to 110 
fathoms per minute, and the imiiact can usually be felt by grasping the towline. 
When the lower net is closed, steam ahead at the usual towing speed and heave in 
at the rate of 25 to 28 fathoms per minute, according to the state of the sea. 
The net has been used successfully in 1,700 fathoms, yet it was looked upon as a 
makeshift. Its principal weakness was due to the action of the sinker d, which was 
necessary in lowering, but caused the net to tow at such an angle that the useful 
area of the ring was greatly reduced, whereas fully three-fourths of the area is 
operative in the improved pattern. 
THE TANNER INTERMEDIATE TOW NET, IMPROVED PATTERN. 
- This apparatus (plate xxxvii) is the same in principle as that already described, 
and its function, the collection of animal life from known intermediate depths, is also 
the same, but its efficiency and certainty of action are increased, and it is more easily 
operated. Its frame is composed of brass pipe and fittings of commercial iiattern, 
carrying a net so arranged with drawstring, movable weights, tripping lines, friction 
clamp, and messenger that its lower part can be closed at will. 
General description. — The ring a is 2 feet 5 inches inside diameter, composed of 
brass pipe I j-g inch outside diameter, bent in a circular form, tke ends joined by a 
union. On the ring are four tees, two on each side, spaced 6 inches apart, and secured 
F. C. B. 1896—24 
