17 



onlji as Hoatp; tlioy can hear the pressure of tlie water cven doAvn to 3000 

 fathoms (cmp. Tanner, loc. cit. p. 355), and do not chauge their specifie grav- 

 ity, such as \Yood or eork, whicli alreadj' on a deptli of a few fatlioms is 

 pressed full of water, and so looses its power of lifting the net. Each glass- 

 balloon can bear about '/.j Ib. of lead in the water, and I have found it suitable 

 to put on just so many balloons that they can bear the tveif/hf, Avhich is tied on, 

 in the irater. The seine will theu sinii on account of the net itself and of the boards. — 



It is a most important thiug that t!ie seine is well balanced, and balanced 

 to fisli on tliat bottom on which we want to use it. It is apt to be too 

 heav3% so that it gets filled with mud. (See ante, however, p. 13, as to the use 

 of a coir-rope). With glass floats, tied up in meshes of 

 spun yarn, the balancing can very easily be managed on 

 shallow water, and the whole apparatus can there be prop- 

 erly arranged. Its specifie gravity will then not change - 



perceptibly on tlie great depths, as with cork or wood. I 

 have found ca. 30 glass-balloons, and a weight of 14 — 1(] 

 Ibs. under water, snitable. 



The boards are made of deal boards, '/j ii^ch thick, 

 with two long iron bolts through them. They are c. 29 inches 

 iiigli and 32 inches long, or longer. At first we used small- 

 er boards, but these fish incomparably better. They are 

 bound with ii'ou below, so that they sink as quickl_y as you 

 want them to. On account of the distribution of the weight 

 (with iron below), they will remain in an upright position wheu they reach the 

 bottom, and they always sink through the water upright, just as the arms of the 

 seine. When they are suspended in the thimble which is placed in their four- 

 branched cro\v-foot, they must point down a little with their fore-end. The ropes 

 of the arms are fastened to the hind-edge of the boards in two holes, so that the 

 arms sit on the oufside of them. From a little in front of the centre of the boards 

 the two bridles of the crow-foot proceed (Cmp. fig. 5 — G.) The latter was made of 

 wire, and each bridle \vas c. 8 fathoms long. At first we used a shorter crow-foot, 

 but it is a great question whether it ougJit not to he still longer. (As to this, see 

 farther on). In the vertex of the crow-foot is a sliackle, in one eye of wliich the 

 tow-rope is fastened. To prevent the bridles of the crow-foot from twisting 

 together, as they are inclined to, a lead (of c. 5 Ibs.) is fastened to the under- 

 most, movable e3'e of the said .shackle, so that it hangs dowuward in a short 

 strap. This prevents the twisting (Cmp. fig. 7). 



As soou as the bag and the arms have got into the water, and tlie boards 



3 



T~ c^^t 



rig. 7. The vertex of 



the crow-foot with 



shaclile and lead to 



prevent twi.sting. — (The 



dotted balloon worlts 



to \he same effect.) 



