574 FISHERIES OF THE UNITED STATES. [62 J 



is of iron, 4 inches wide by three-eighths of an inch thick, and is bent 

 in the middle to form a right angle. At the outer end there is a small 

 immovable ring, and at the upper end a very strong n -shaped eye 

 bolted on for suspending the block. The center pin or bolt is of steel 

 and passes through the strap at the angle, having a nut at each end. 

 The friction rods are six in number, 2£ inches long by 1J inches in 

 diameter, and are suspended in a circle between two flat rings, one at 

 each end, by means of a pin passing loosely through each rod and fast- 

 ened into the rings. The rods are therefore free fco revolve, independ- 

 ently of one another, though they touch slightly. This friction-rod ar- 

 rangement, which is entirely of brass, fits snugly into the center hole of 

 the sheave, and in turn receives the steel pin which serves as the axis 

 for the sheave. 



Safety Hooks, for attaching the beam trawl to the wire dredge-rope and 

 releasing it in case of undue strain from fouling on the bottom. 

 Eepresented by photographs. 



United States Fish Commission. 



" The safety hooks are designed for the purpose of detaching the 

 trawl when, from any cause, such as fouling a rock or wreck, the tension 

 on the dredge-rope reaches the limit of safety. They consist of a stout 

 steel spring inclosed in an iron cylinder and controlling the opening 

 and closing of a pair of heavy 4 iron hooks, which project from one end, 

 and can be adjusted to detach at any point between 3,000 and 6,000 

 pounds, by the nut on the end of the central rod. As used on the 

 steamer Fish Hawk, they were set at 4,000 pounds, the breaking strain 

 of the dredge-rope being 8,700 pounds. The details of construction are 

 shown in the photographs. The spring and hooks being placed in the 

 cylinder and the cap screwed on, the instrument is ready for use. The 

 end of the dredge-rope is spliced into the eye and the trawl shackled 

 to the hooks, which are held in position by their shoulders pressing 

 against the inner surface of the cylinder. The spring is compressed as 

 the tension increases until the limit of safety being reached the shoul- 

 ders are released and the hooks open freely, allowing the shackle pin to 

 slip through, detaching the trawl and relieving the rope from strain." 



APPLIANCES FOR THE EXAMINATION AND STORAGE OF 

 ZOOLOGICAL MATERIALS. 



Table or Deck Sieve, for washing the contents of the beam trawls. 



United States Fish Commission. 



" This piece of apparatus is the result of several successive improve- 

 ments, and was given its present form in 1877. It has been the joint 

 invention of Prof. A. E. Verrill, Capt. H. C. Chester, and Mr. James E. 

 Smith, of the United States Fish Commission. In fundamental princi- 

 ple it is like the cradle sieve much enlarged and raised on legs, but the 



