HOW THE SEA IS SOUNDED. 



337 



the sinker to pass swiftly to the bottom. While the apparatus 

 for sounding the sea consisted of a weight secured to the end of a 

 hempen cord which was paid out from a simple reel on the deck 

 of a vessel, no reliability could be attained in the measurement of 

 depths, because the cord employed was necessarily so large as to 

 become a controlling element in the weight of the system. But 

 when the project for the Atlantic telegraph 

 cable made it necessary to obtain accurate 

 measurements of the depth of the ocean, 

 Midshipman Brooke, of the United States 

 Navy, took the first great step 

 in providing means for trust- 

 worthy deep-sea sounding by 

 inventing an implement in 

 which the sinker, en- 

 veloping a tube se- 

 cured to the sounding 



FIG. 4. THE SIOSBEE DEEP-SEA 

 SOUNDING MACHINE. 



line, was detached on striking the bottom and left behind when 

 the tube was drawn .up. 



The modern form of deep-sea sounding cylinder, which is the 

 result of the experience of Commander Sigsbee, of the United 

 States Navy, during his great work in developing the orography 

 of the Gulf of Mexico, is provided with valves at the upper and 

 lower ends which open upward, and during the descent allow 



