572 FISHEEIES OF THE UNITED STATES. [60 J 



Sigsbee's improved Dredging Accumulator for relieving the strain on the 

 dredge rope; devised by Commander Charles D. Sigsbee, (J. S. N. 

 United States Fish Commission. 



The construction of the accumulator used by the United States Coast 

 Survey and Fish Commission in connection with the dredging gear is 

 shown on Sigsbee's plate No. 34. "This apparatus consists of a num- 

 ber of rubber buffers A A, arranged for compression on a rod B, and 

 separated from one another and the rod by guide-plates C C. The up- 

 per end of the accumulator being secured at D, and a strain applied to 

 the lower end at E, the compression of the buffers will permit the cross- 

 Tiead F to travel along the rod B, and the rods G G to travel through 

 the guide-plate H and the cross-head I. In this manner the accumu- 

 lator elongates under strain, and when released from strain is restored 

 to its former length by the elastic force of the buffers." In this form 

 of accumulator, which was devised in 1878, by Commander Sigsbee,, 

 for use on the Coast Survey steamer Blake, the only new feature 

 claimed by the inventor is the peculiar shape of the guide-plates C C, 

 the hubs or fillets of which keep the buffers from coming in contact with 

 the rod B when the buffers are compressed. The buffers are 4£ inches 

 wide and 3 inches thick, and have a circular hole through the center 1^ 

 inches in diameter. They are made of what is known as compound No. 24, 

 consisting of 10 pounds of fine Para rubber, 1 pound of white lead, 1 

 pound of litharge, 1 pound of whiting, and 10 ounces of sulphur, the 

 vulcanizing heat being about 260° Fah. A somewhat harder compound 

 than this has, however, been recently employed. The long rods, nuts, 

 cross-heads, and large guide-plate are of steel ; the small guide-plates 

 between the buffers are of brass, and all the other metal parts of wrought 

 iron. The small guide-plates are one-eighth of an inch thick, and their 

 hubs are made to fit loosely upon the rod and tightly within the buffers. 



The accumulator recently constructed for the Fish Commission steamer 

 Albatross is of exactly the same pattern and size as that employed on 

 the Blake, but on the steamer Fish Hawk a slightly smaller one is in 

 use, differing from the others, however, only in length and in the num- 

 ber of buffers, the size of the latter being the same. The example dis- 

 played is copied from that of the Fish Hawk. 



In the Blake accumulator the central rod accommodates thirty-two 

 buffers without compression, but seven more are pressed on, in order 

 that the accumulator may not extend for a light strain, Commander 

 Sigsbee explaining that " neither an accumulator nor a dynamometer 

 is of use excepting for a severe strain." The maximum extension of 

 this accumulator is about six feet. The Fish Hawk accumulator con- 

 tains only twenty-six buffers. 



In Sigsbee's series of plates, the accumulator is shown in position 

 for use, suspended from the mast-head, in Plates 1 and 24; and lowered 

 into view in Plates 13 and 14.. In the photographic views of the Fish 

 Hawk it is also shown in rdace. 



