568 F1SHEKIES OF THE UNITED STATES. [.00} 



to a wrouglit-iron frame, has a flap or clapper valve opening inwards and 

 fastened to the shorter arms of a set of levers. The upper end of the 

 cylinder is cohered with a removable wire sieve (60 wires to the inch),, 

 and inside the cylinder are a wire sieve (27 wires to the inch) and a 

 wire funnel or trap (27 wires to the inch). The steel-wire rope on 

 which the cylinder travels is placed in loops at the upper and lower 

 extremities of the frame, and is retained therein by screw-bolts. 



The friction clamp is composed of a solid frame, two binding chocks, 

 a clam ping screw, and an eccentric trigger or tumbler. The friction buffer 

 is composed of a solid frame, two binding chocks, a clamping screw, and 

 a compression spring with a regulating screw for regulating the binding 

 force of the spring. The bearing faces of the binding chocks are cor- 

 rugated, and the inward movement of each is limited by a stud which 

 forms part of the frame. In clamping the buffer to the rope, the chock 

 next the clamping screw is always screwed inwards until stopped by its 

 stud; the steel rope is, therefore, always pressed between the two chocks 

 by the elastic force of the spring, which may be regulated as desired. 

 To regulate the buffer for any definite frictional resistance, clamp it to 

 the rope and move the regulating screw well inwards; then suspend 

 from the buffer a weight equal to the resistance decided upon. Move 

 the regulating screw outwards until the buffer slides down the rope r 

 under the influence of the suspended weight. Since the chock operated 

 by the clamping screw is always screwed "home" in clamping to the rope,, 

 the buffer remains regulated for prolonged use, and it is probable that 

 the regulating screw need not be touched again for a whole cruise, if the 

 buffer be rinsed in lye- water each time after use. 



A cast-iron messenger in two parts, connecting with each other by a 

 dovetail, is an important part of the apparatus. Professor Agassiz 

 added the funnel-shaped trap, after a preliminary trial with the appara- 

 tus. 



Working the apparatus. — It is necessary to first regulate the buffer to 

 cushion the stoppage of the falling weights, which are, cylinder and 

 frame 38 pounds, clamp 4 pounds, messenger 8 pounds, total 50 pounds. 

 The Blake adopted a resistance of about 80 pounds (this resistance 

 being, of course, constant during the whole movement of the buffer), it 

 having been found that a blow of that force resulted in no injury to the 

 apparatus. 



On the ascent the buffer must withstand not only the weight of the 

 50 pounds of metal, but also the resistance which the water offers to 

 the passage through it of the several parts of the apparatus. Moreover, 

 when the cylinder emerges from the water it is full of that liquid, and 

 with this increased weight would overcome the stated resistance of the 

 buffer and force the latter downwards until the lead was reached. To 

 meet these conditions it was not thought advisable to increase the re- 

 sistance of the buffer, which would involve a heavier blow against the 

 apparatus, but a rope-yarn seizing or stop was placed on the rope, about 

 15 or 20 feet below the buffer, beyond which the latter could not pass. 



