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HISTORY OF THE SEA. 



rope holding up the movable arms, they fall, disengage the 

 ends of the sling, and allow the ball to slide down the rod. 

 The rod is then withdrawn, carrying up the portion of the 

 bottom secured in the cavity at its foot, and leaving the ball 

 on the bottom. This apparatus costs a ball each time- it is used, 

 and brings up but a small portion of the bottom, which is also 

 apt to be diminished on its way to the top, by the water it 

 passes through. 



Commander Dayman, of the English Navy, in 1857 invented 

 an improvement upon Mr. Brooke's original invention. lie 

 used iron wire braces to support the sinker, as these detach 

 more easily than slings of rope. The shot he replaced by a 

 cylinder of lead, as offering less surface to the water in its de- 

 scent, and he fitted the cavity in the bottom of the rod with a 

 valve opening inward. Commander Dayman used the appa- 

 ratus, with these modifications, in the important series of 

 soundings he made in the North Atlantic, while engaged in 

 surveying the plateau for the ocean telegraphic cable, and re- 

 ports that it worked well. 



The apparatus known as the bull-dog machine is an adap- 

 tation of Sir John Ross' deep-sea clamms, together with 

 Brooke's idea of disengaging the weight. It was invented 

 during the cruise of the English Navy vessel, the Bull-dog, in 

 1860, and the chief credit for it belongs to the assistant engineer 

 during that cruise, Mr. Ste.il. A pair of scoops are hinged 

 together like a pair of scissors, the handles represented by B. 

 These are permanently fastened to the sounding rope, F, which 

 is here represented as hanging loose, by the spindle of the 

 scoops. Attached to this spindle is the rope, D, ending in a 

 ring. E represents a pair of tumbler hooks, like those used 

 so generally. C is a heavy weight, of iron or lead, hollow, 

 with a hole large enough for the ring upon D to pass through. 

 B is an elastic ring of India rubber, fitted to the handles of 

 the scoops, and designed to shut them together as soon as the 



