MUSEUM OF COMPARATIVE ZOOLOGY. 47 
cloth. The net is lowered with the open frame (as represented in Fig. 1) 
uppermost, at the rate of about 100 fathoms in four minutes; when 
the net reaches the requisite depth at which it is to be towed, sufficient 
slack of wire is let out, so that the angle of the wire rope due to the 
speed of the vessel will keep the net towing at a nearly uniform depth, 
It is usually towed for twenty minutes, when the speed of the vessel is 
slackened, as the rope is wound in, until the net is vertical when the 
ship stops; the messenger, m (Figs. 1, 2), is then sent down on the 
wire rope, and, striking the crank ¢, trips it, and it drops to the posi- 
tion ¢’, as seen in Figure 4. This liberates the loops of the string //, 
by which the weights ww are hung; these drop rapidly to the position 
ww, as seen in Figure 6, pulling both together, and closing tightly the 
loop which passed round the lower part of the net. The net is then 
hauled up at the same speed at which it was lowered, and invariably 
comes to the surface with the bottom part tightly closed. The upper 
part of the net above the loop remains open, and collects anything found 
on its way from the depth at which the towing was made to the surface. 
When the net reaches the surface, the loop closing the net is at once 
supplemented by winding below it a stout twine; the bottom fastening 
of the net is then opened, and the inside net carefully washed in filtered 
sea water, and that in its turn carefully examined. 
Figure 2, the messenger m (made in halves), showing the grooves, s, 
by which it is fastened to the wire rope 7. 
Figure 3, the extremity of the dredging-wire rope, with its weight, 
from which the net is suspended. 
Figure 4, showing the clamp attached to the wire rope 7, with its 
crank, ¢, from which are hung the loops of the line /, holding the 
weights ww suspended ; ¢’ shows the position of the crank after it has 
been tripped by the messenger m. 
Figure 5, the same as Figure 4, seen from above. 
It will be noticed that we used no contrivance by which the Tanner 
net was sent down closed, and subsequently opened when at the required 
depth. To obviate this difficulty, we loaded the wire rope with a heavy 
shot, a (Figs. 1, 3), to counterbalance its weight, and in addition attached 
to the bottom of the guides of the Tanner net a heavy weight, b (Figs. 
1, 6), so that, when lowering the apparatus slowly, the net was sent 
down with the closed extremity leading. In this way the pressure of 
the water on the bag of the net kept the lower part of the sides closely 
compressed together. Water passed through only the upper open parts 
of the net, close to the mouth frame, where the meshes are those of an 
VOL. XXIII. — NO. 1. 4 
