[19] CONSTRUCTION AND WORK OF FISH-HAWK. 21 



to the surface mollusks and various other forms living a few incheai 

 under the mud or sand of the bottom. 



The Blake dredge is usually preferred for use with the rake as it skims 

 over the bottom lightly, picking up what has been turned up by the 

 rake without overloading itself with mud. 



THE TANGLE BAR. 



The form of tangle bar used by the Commission was devised by Prof. 

 A. E. Verrill in 1873, and consists of an iron bar supported at each end 

 by a fixed wheel, or iron hoop. Six chains are attached to the bar at 

 intervals of one foot, and they are about 12 feet in length. To these 

 chains are secured deck swabs or bundles of rope yarn at intervals of 

 about 18 inches. The apparatus is shown in Plate X, partially sus- 

 pended under the main boom. It is very useful on rocky bottoms where 

 it will capture specimens when no other device could be made available. 



THE TABLE SIEVE. 



Plate XI shows the table sieve, as used by the Commission. The 

 hopper, with its coarse wire-gauze bottom, is seen in the foreground, 

 then the fine wire-gauze tray which rests beneath it, and finally the 

 table itself with its canvas bottom and hose from which the waste- water 

 is conducted to the scupi)er. This device is peculiar to the United 

 Stiites Fish Commission, and has probably contributed as much towards 

 its success in deep-sea exploration as any single implement used. To 

 prepare the table sieve for service, the tray is placed in position, then 

 the hopper when it will assume the form shown in Plate XII. The con- 

 tents of the trawl (a mixture of mud and various forms of marine Life) 

 being emptied into the latter, a stream of water is turned upon the mass 

 and the work of collection and assortment commences. The larger 

 forms are taken from the hopper, the smaller ones from the tray, while 

 the more minute and delicate specimens are found on the canvas bottom. 



THE CRADLE &IEVE. 



The cradle sieve is designed to receive the contents of the dredge, as 

 the table sieve does that of the trawl. It is semicircular in form, as 

 shown in Plate XI; the bottom and sides being composed of a coarse 

 wire-gauze, lined with the same material, but very fine; the tray or 

 hopper has also a coarse gauze bottom. 



To prepare the cradle sieve for use, the hopper is placed in position 

 and the sieve hung over the side, abreast of tbe dredging port. The 

 contents of the dredge being emptied into it, a stream of water, strong 

 or light as desired, is turned on as with the table sieve, the collection 

 and assortment being carried on in a similar manner. 



DREDGING ARRANGEMENTS, MAIN DECK. 



Plate XII shows a portion of the starboard side of the main deck as 

 arranged for dredging. The table sieve is seen standing abaft the 



