Life of the Waters 365 



machine, in which a counter-weight serves to check quickly 

 the speed of the wire, when the sounding weight reaches the 

 bottom. The types employed by the "Albatross" and other 

 vessels of the U. S. Bureau of Fisheries, in which adjustable 

 springs are used as brakes, instead of counter-weights, are 

 known as the Sigsbee and Tanner machines from their 

 designers, Commanders C. D. Sigsbee and Z. L. Tanner of 

 the U. S. Navy. These springs also serve as "accumulators" 

 to relieve sudden strains on the sounding line, due to tossing 

 of the ship in rough weather. 



Another means of checking the descent of the line is the 

 detachment of the sinker when the bottom is reached. This 

 is usually accomplished by means of a catch to which the 

 sinker is attached. While the sounding line is taut this 

 catch is automatically held in place, but when the former 

 is slackened the catch drops, releasing the sinker and thereby 

 relieving the pull on the line. 



For taking samples of the bottom there is frequently 

 attached below the sounding weight a metal tube lined with 

 tallow, which is driven into the bottom by the impact of the 

 sinker, and when drawn up retains some of the bottom 

 material adherent to the tallow. Some samplers are made 

 with valves at the upper and lower ends of the tube, which 

 are automatically closed when the sample is taken, thereby 

 preventing the escape of the catch. For taking larger sam- 

 ples of the bottom, devices similar to the ordinary grapple- 

 dredge used in excavation work are sometimes employed. 



The measurement, of ocean currents is made with various 

 types of current meters, some of which are constructed on 

 the principle of the instrument used by the U. S. Weather 

 Bureau for measuring the velocity and direction of the wind. 

 These carry a vane or rudder for holding the meter in line 

 with the current, and a series of revolving cones, the number 

 of revolutions of which are transmitted by a telephone to 

 the ear of the observer at the surface, and from their number 

 per minute the velocity may be computed. In the Eckman 

 current meter named from the Swedish naturalist, V. W. 

 Eckman, which is much in use, both here and abroad, the 

 velocity of the current is registered by the revolutions of a 

 propeller, connected to a dial whose hands are turned by a 

 set of cog-wheels, and the direction recorded by means of a 

 magnetic needle, a box divided into thirty-six compartments, 

 and a tube full of shot connected to one of the cog wheels 

 of the dial. As the latter turns it feeds the shot into the 

 needle box where it falls onto the middle of the needle, and 

 then runs through a groove to drop into one of the thirty- 

 six compartments, depending upon the position of the needle 



