42 



THE MUSEUM. 



THE SINKER. 



ments was solved. That is to say, the 

 explorers found that piano wire of 2 i 

 American guage (.028 of an inch in 

 diameter) had a uniform tensile strength 

 sufficient to bear 200 pounds without 

 breaking. Moreover, it was very flex- 

 ible, was highly polished and was not 

 easily rusted. Further than that, it 

 was a very light weight cord for its 

 strength, 100 fathoms weighing a trifle 

 less than one pound and a third; the 

 weight of the length to reach the deep- 

 est valley yet found in the sea — more 

 then five and a half miles from the 

 surface — was but sixty-three pounds. 

 Having discovered a line that was 

 practically perfect for the purpose, a 

 machine for handling the line and sink- 

 er had to be devised. A Yankee naval 

 officer. Commander C. D. Sigsbee, has 

 the honor of having invented the best 

 thing of the kind. It is a very simple 



affair. There is a reel that is 22. 89 

 inches in diameter, so that one turn 

 gives exactly a fathom of wire. The 

 wire runs from the reel to a guide pul- 

 ley that is suspended on long springs, 

 and thence into the sea. The guide 

 pulley is suspended on sprjngs because 

 the vessel is sure to jump and roll a- 

 bout, and so jerk the wire about when 

 the crew are sounding. The springs 

 are at once powerful and easy enough 

 to take up the strain on the wire. An- 

 other important purpose served by 

 these springs is to indicate when the 

 sinker reaches the bottom. The mom- 

 ent they are relieved of the weight of 

 the sinker they jump the guide pulley 

 up in a way not to be misunderstood. 

 For the rest, there are a brake to stop 

 the paying out of the wire when bot- 

 tom is reached, an engine to reel in the 

 wire, and a dynamometer to show the 

 strain on the wire. The whole stands 

 on a platform rigged outboard, where 

 the sinker and wire can run clear of 

 all. 



For a sinker merely to measure the 

 depth any old-style cannon ball would 

 do, but since a specimen of the soil 

 encountered is wanted, and the tem- 

 perature of the water down at the bot- 

 tom as well, a somewhat more elabor- 

 ate sinker has been invented, the one 

 in common use being the product of 

 the experiences of Commander Sigsbee 

 and Admiral Belknap, whose work in 

 the Pacific. There is first of all a 

 big iron ball or shot with a two-inch 

 steel pipe running loosely down 

 through its center and projecting .some 

 distance below. The pipe is securely 

 fastened to a knuckle-jointed hook on 

 the end of the sounding wire, but the 

 big hollow shot hangs on the hook by 

 a bail. The shot drops down until it 



