CHAPTER VI 

 THE SEA FLOOR 



BY SIR JOHN MURRAY 



Methods. The oldest method of sounding was by 

 means of the hand-lead, usually 12 to 14 pounds in 

 weight, " armed " with lard or tallow, to which a 

 sample of the bottom adheres, and with a line marked 

 in fathoms and fractions of a fathom. Practically 

 all the coasts of the world have been surveyed by 

 instruments of this kind used from rowing-boats. 

 When attempts were made to sound in 100 or 200 

 fathoms, heavier weights and more carefully prepared 

 hempen lines were employed, and the leads were pro- 

 vided with cups, valves, or snappers, to bring up 

 samples of the sands, gravels, and muds. Sir James 

 Clark Ross, during his Antarctic cruise (1839 to 

 1843), made most praiseworthy attempts to sound 

 the greater depths of the ocean with ordinary sounding 

 lines and heavy weights from small boats. He 

 succeeded in recording depths down to 3,600 fathoms, 

 but, although the time each 100 fathoms left the reel 

 was noted in the usual way, he was uncertain when 

 the weights reached the bottom, and the results were 

 not altogether trustworthy. About the year 1854 

 Lieutenant Brooke, of the United States Navy, intro- 

 duced the method of detaching a heavy weight from 

 the sounding-tube on its striking the bottom ; hence- 

 forth deep soundings were recorded much more fre- 



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