HINTS FOR COLLECTING. 233 



ring is attached to the rope by a " stop " or bit of 

 spunyarn, which is slack enough to break in case the 

 dredge catches : the stop is then snapped asunder, and 

 the dredge, hanging on one side, is set free and hauled 

 up. In order to give timely warning of the dredge 

 being caught, and to ascertain the degree of tension to 

 which the rope is subjected, the upper part of the rope 

 is attached to the bulwarks by india-rubber springs 

 called " accumulators." When the dredge has been 

 working from half an hour to two hours (the time being 

 regulated by the depth and nature of the ground) , the 

 rope is passed through a moveable block fixed to the 

 shrouds, and hauled in by means of a double winch or 

 drum; in a boat this is done by hand. The contents 

 of the dredge should be emptied gently and carefully on 

 a piece of tarpaulin. The sieves then come into requi- 

 sition ; and these are indispensable for examining the 

 results. They are usually made of copper wire, and 

 should be of four or five different sizes, fitting one into 

 another or "nested," the coarsest sieve being uppermost. 

 The most convenient sizes of the meshes are J, |, ^, y 1 ^ , 

 and ^ inch. The frame should be of oak or some other 

 wood which will not swell in water. Each of the lower 

 sieves should have a ledge on the inside about an inch 

 from the bottom, to receive the one above it, the finer 

 stuff which passes into it being thus protected from 

 pressure. The diameter of the top sieve may be 10 or 

 12 inches, and the outer rim 3 or 4 inches deep. The 

 top and bottom sieves should be strengthened by cross 

 bars of copper. The stuff should be sifted in a tub of 

 seawater; and after it has been looked over, so as to 

 secure any living specimens for more careful examina- 

 tion or dissection, the residue may be put into bags, 

 dried on cloths in the open air, and afterwards resifted. 



