570 BE. G. H. FOWLER OX THE [June 21, 



As a inid-water net has to be drawn up by a steam-winch more 

 rapidly than is usual with a surface tow-net, even when the winch 

 is gomg its slowest, boulting cloth of twenty-five (1896) and forty 

 (1897) meshes to the inch was selected; of these the second is 

 stronger and more efficient. If the windiog-drum can be run dead 

 slow by gearing, 50 or even 60 meshes to the inch might be used. 

 A calico baud at tlie mouth pierced by lacing-holes, and a calico 

 band at the cod-end, with a tape by which the collecting zinc pot 

 is tied in, complete the net. The tape should run in loops outside 

 the calico band, it is there much easier to untie with cold wet 

 fiugers. 



The net-frame (tig. 1, where it is represented as half open) 

 consists of t\\ o | — ! — | shaped phosphor-bronze castings BB' hinged 

 together on a solid brass axle C ; on to the latter is also hinged, 



outside BB', a wrought iron | 1 shaped piece A, which is rather 



larger than the other two. The arms bb of BB' are drilled to take 

 shackle-bolts from which chains pass upward to the locking-gear ; 

 two holes are also drilled at aa for similar shackle-bolts and chains. 

 The net-frame in its descent is suspended from bb, and is therefore 

 tightly closed by its own weight (about 15 lbs.) and by any additional 

 weight that may be hung on the axle, the arms pi-essiug BB' firmly 

 together ; when the chains from bb are slacked by the locking-gear, 

 the net falls for a short distance, the weight is caught on to the 

 chains from aa, and the net-mouth either falls open, or opens on 

 the slightest pull in towing. The whole apparatus is then 

 hauled upwards through the zone which it is desired to investigate 

 (generally 100 fathoms). The chains from aa are then slacked by 

 the locking-gear, the net falls a second time, and the weight, being 

 caught on the chains from bb, again closes the net effectively. 



In fig. 2 the sectional dimensions of A, B, B' are given, the net- 

 frame being represented as closed. The upper end of the net 

 itself, laced inside the frame, is compressed into the space between 

 B and B' ; the dotted lines indicate the lacing-holes drilled 

 through the frame at intervals of an inch. When it is closed, only 

 a Protozoan could get through the net-mouth, and even that would 

 fiud a difficulty. — B and B' when open form a mouth twenty inches 

 square (inside measurement) ; A is | inch outside them when closed. 

 The arms bb are seven inches long, and effect a good leverage for 

 closing the net. They form one of the most important improve- 

 ments on the original pattern. Even shaking the frame violently 

 up and down ^^he^ held by the chains does not open the net. 



[The locking-gear of the 1896 pattern was arranged as follows : — 

 Through the chains from aa and bb were passed the hammers of 

 two reversed gun-lock movements, the hammer rising when fired ; 

 the lock of the bb chains was placed vertically below that of the 

 aa chains. Parallel to the vertical between these two ran a long 

 steel rod, tapped with a screw-thread : at the lower end of the 

 steel rod was a screw-propeller, arranged so as not to revolve 

 during the descent of the apparatus. When hauled upwards, 

 however, the propeller began to revolve, travelled up the steel rod. 



