EQUIPMENT. 11 



and on striking bottom the bail is prevented from getting over 

 the top of the detacher by the bearing which the sinker has 

 against the under part of the cone. 



When the sinker strikes bottom the slacking- of the soundino-- 

 line or wire trips the tumbler, and the sinker is free to slide off 

 the cyHnder. This tumbler is kept back by the spring JV, and 

 the bail cannot be rehooked when the line is hauled taut to reel 

 in. The resistance of the bottom soil raises the poppet-valve F, 

 and the specimen of the bottom enters the cylinder, the water 

 within the cylinder being free to escape through the various 

 perforations P, P, etc. On hauling back the poppet-valve falls, 

 or is forced by its spring, H, to the valve-seat, and the cone / 

 falls, closing the water apertures. When the rod has been got 

 on deck the lower part of the cylinder is unscrewed, when the 

 specimen of soil may be extracted. To prevent the wire from 

 coiling on the bottom, a piece of rope somewhat less than quar- 

 ter of an inch in diameter, and from nine to twelve fathoms lonsr 

 (the stray line), is spliced to the wire, and to this is attached the 

 sinker, detacher, and any instrument sent down while making a 

 soundino\ 



The great advantage of sounding with wire is in the very 

 great strength of the wire as compared with that of stout cod- 

 line ; also in the smoothness of its surface, by which the friction 

 is reduced to a minimum ; so that a wire weighing, say, twelve 

 pounds in water to the mile, can readily take down a hundred- 

 pound shot, and not only bring up the fourteen pounds weight 

 of the sinker and collecting cylinder, but carry besides the 

 thermometers needed to ascertain the temperature both of the 

 bottom, and of intermediate depths as well. It would, however, 

 in practice be more convenient to use a separate reel, and ^vire 

 slightly heavier for making the temperature observations, and 

 for having the water-cups attached. 



The weight of the wire payed out in the deepest soundings yet 

 made, 4,655 fathoms, will, in water, be less than sixty pounds, so 

 that the weight of the sinker (one hundred pounds or more) can 

 always be made to exceed that of the wu-e, an impossibility in 

 the case of soundings made with hemp-lines. So far as accuracy 

 is concerned, everything also is in favor of the wire method. 

 The time of striking bottom is determined, not as in the case of 



