THE 



POPULAR SCIENCE 

 MONTHLY. 



JULY, 1873. 



HOW THE SEA-DEPTHS ARE EXPLORED. 



ONE of the most recent and impressive examples of the interac- 

 tion of science and art by which knowledge is extended, and 

 man's control over Nature increased, is furnished by the late remark- 

 able investigations into the depths and life of the sea. The taking of 

 soundings is, of course, as old as navigation, and is an indispensable 

 portion of the mariner's art. The record of these soundings was em- 

 bodied in charts by which sailors were guided in unknown waters. 

 As commerce extended, such observations became more full, and re- 

 sulted in systematic coast-surveys in which the depth of water, cur- 

 rents, magnetic conditions, temperatures, tides, and winds, were taken 

 into account, and the knowledge thus accumulated gave rise at length 

 to a great science the Physical Geography of the Sea. About 

 twenty-five years ago a new step was taken toward the extension of our 

 knowledge of sea-depths. Science had given to the world the electric 

 telegraph, and commerce demanded that it should be laid across the 

 ocean. For this purpose the bed of the North Atlantic required to be 

 carefully examined and mapped, and the configuration of the sea-bot- 

 tom and the nature of its material determined. This gave a new im- 

 pulse to the art of sea-sounding. The transatlantic cable was laid, 

 got broken, and the end of it was then fished up from a depth of 

 nearly two miles. A great victory was thus gained ; the bottom of 

 the sea was no longer inaccessible, and the possibility of its scientific 

 exploration became established. Hitherto, sea observations had main 

 reference to the advantages of navigation and commerce; but, from 

 this time forward, the idea was entertained of pursuing the investiga- 

 tion in the interest of science alone. At the instance of the Royal 

 Society, the British Admiralty, in 1868, granted a small government 

 vessel, the gunboat Lightning, to Dr. William B. Carpenter and Prof. 

 Wyville Thomson, to be used for dredging the bottom of the sea, 

 and investigating its animal life. So promising were the results of 

 vol. m. 17 



