284 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



one-tenth, of a square metre, to which are attached three 

 iron rods, each 40 cm. long, which are in tnrn attached to 

 another broad and flat iron ring, d, of 100 cm. diameter. 

 The iron rods are at their upper ends bent into hook-like 

 rings, to which ropes are attached. The whole of this 

 head piece is covered with fnstian. This part serves to 

 prevent mnd or slime getting into the net when it is 

 lowered on to very soft ground. The edge, d, sinks to 

 some extent in the mnd, bnt only when the edge, e, sinks 

 below the surface of the mnd can the latter enter the net. 

 Only very occasionally was the head piece found to be not 

 sufficiently high. It is also useful, as it serves to 

 prevent part of the catch from overflowing the ring d, for 

 instance, should the ship during the time the net is out 

 sink to the trough of a wave, the net might at the same 

 time be raised and its contents be spilt. The net is also 

 liable to collapse in a short choppy sea. The space in 

 the headpiece serves to prevent these accidents, as the 

 volume of water momentarily jerked out of the net proper 

 is retained in this space and subsequently filters through 

 the net itself. To the iron ring, d, is suspended a rope 

 sewn on with linen, and from this the silk net passes to a 

 brass ring. The net has a funnel-shaped form. An 

 improvement would be effected if it were possible to make 

 it cylindrical. 



To the brass ring, f, a filtering cylinder or bucket is 

 suspended. After many experiments Hensen came to 

 the conclusion that the most suitable material for the net 

 itself was silk bolting cloth or gauze ("Mullergaze"), being 

 the material used by millers to separate flour of different 

 qualities. This silk bolting cloth is numbered according 

 to the meshes of the silk. There are twenty varieties, of 

 which the highest number has the smallest mesh. The 

 web is very ingeniously constructed, so that the threads 



