October 24, 1884.] 



SCIENCE. 



403 



on the steamer Blake, in 1878. It consists of 

 a number (26 to 37) of rubber car-buffers, ar- 

 ranged for compression on a central rod, and 

 separated from one another b}' thin brass guide 

 plates provided with hubs or fillets, which 

 prevent the buffers from coming in contact with 

 the rod. Under strain applied at the lower 

 end, the accumulator elongates, and when re- 

 leased from strain is restored to its former 

 length by the elasticity of the buffers. The 



Fig. 3. — Sigsbee's ACCU- 

 MULATOR FOR DEEP-SEA 

 DREDGING, WITH DREDGE- 

 BLOCK ATTACHED. 



Fig. 4. — The safety- 

 hooks FOR ATTACH- 

 ing the beam-trawl 

 to the drag-rope. 

 Shown in detail. 



amount of extension afforded by the Blake's 

 accumulator was six feet, which, according to 

 the experience of Commander Sigsbee, is quite 

 sufficient ; the principal purpose of an accu- 

 mulator being to indicate the amount of strain 

 after fouling, and when the dredge-rope has 

 been hauled tight and is nearly vertical. The 

 English accumulator, consisting of a number of 

 long elastic rods, was intended to relieve the 

 first strain upon the rope in case of fouling. 



The safety-hooks (fig. 4) invented by Capt. 

 Tanner, U.S.N. , are an ingenious device for 



releasing the beam-trawl in case of its fouling 

 irretrievably, and thus relieving the strain upon 

 the rope which might otherwise break at some 

 distance above the bottom, thereb}' entailing an 

 additional loss of rope. They consist of a stout 

 steel spring enclosed in an iron cylinder, and 

 controlling the opening and closing of a pair of 

 heavy iron hooks, which project from one end, 

 and can be adjusted to detach at an}- point be- 

 tween three thousand and six thousand pounds. 

 Commander Sigsbee first improved the dredg- 

 ing-blocks. In the deck-blocks, the side plates 

 are free to revolve ; but in that which hangs 

 pendent from the boom end, the}' are pinned 

 to the strap, and connected by socket-bolts, 

 which are intended to prevent the dredge-rope 

 from getting between the side plates and the 

 strap. The clredging-blocks supplied to the 

 Albatross have no side plates ; and the sheave, 

 which is of brass, revolves on a series of brass 

 friction-rods surrounding the steel pin or axis. 



Sieves. 



Convenient sieves for working over the mixed 

 materials after they have been landed upon the 

 deck are very important adjuncts to the dredg- 

 ing work. 



The larger proportion of the contents of the 

 dredge and trawl frequently consists of mud or 

 sand, which requires to be washed from the 

 specimens before they can be preserved or 

 studied. Many different devices to accomplish 

 this sifting or washing have been tried, both 

 in this country and in Europe : but of those 

 now emplo} ed b} T the Fish-commission, only one 

 has been borrowed ; the others, two in number, 

 having originated with this surve}'. The three 

 patterns of sieves are intended for different 

 purposes. The simplest is a nest of circular 

 sieves similar to those figured in Sir Wyville 

 Thomson's 'Depths of the sea,' and used for 

 sifting small quantities of material by hand, in 

 a bucket or tub of water. 



The rocker or cradle sieve (fig. 5) is designed 

 especially for washing the contents of the 

 dredges ; and the table sieves, for the great 

 mass of material which so often comes up in 

 the trawl ; but the latter has been found so 

 useful for all kinds of work that it is now most 

 commonly employed, especially as it forms 

 in itself a large and convenient sorting-table 

 around which a number of persons can stand 

 at a time. The cradle sieve was devised by 

 Professor Verrill in 1872, to afford the means 

 of rapid washing over the side of the vessel. 

 It is semic3 7 lindrical in shape, the curved bot- 

 tom and sides consisting of two thicknesses of 



