




108 LIVERPOOL BIOLOGICAL SOCIETY. 
should be payed out to allow the net to reach the required 
depth, when the boat is going at the working rate. 
The speed of the vessel is then reduced so that the 
net gradually sinks to the level which it is desired to 
investigate. 
The first messenger is then allowed to descend, which 
striking upon the pin (g’.) raises the pin (0’.) and liberates 
the loop (7.) in the manner already described. The links 
(h. and 7.) now stretch out, and thus the closing line is 
lengthened to the extent of some three feet. The strain of 
the net is thus borne by the links (¢. and d.), and the 
pressure of the water, aided by the weight on its lower 
margin, opens the net. The present state of matters is 
that shown in fig. 1, and in this position the net is dragged 
so long as its controller thinks fit. 
When this period has elapsed the second messenger is — 
allowed to descend, which strikes upon the pin (g.) raises 
b. and liberates the loop (e.). The opening line is thus 
lengthened by the addition of the cord or chain (n.), in 
consequence of which the strain of dragging the net once 
more falls upon the closing line and the net shuts. 
It is then drawn up to the surface, and the contents 
treated in the usual manner. 
When the tow-net is to be worked in conjunction with 
the dredge or trawl, this latter is first put over, and the 
lock is made fast to the line at any desired distance above 
it, the two cheeks being separated so far as to allow the 
rope to pass in between them. 
Futhermore it will be readily seen that by means of this 
apparatus several tow-nets can be worked at different 
depths on the same rope. The first and deepest is attached 
quite in the usual manner. Just below the lock of the 
next tow-net two messengers are placed upon the wire, 
the “‘first”’ of the pair below the ‘‘second.” ‘The former 

