CHAPTER V. 



DEEP-SEA SOUNDING. 



The ordinary Sounding-lead for moderate Depths. — Liable to Error 

 when employed in Deep Water. — Early Deep Soundings un- 

 reliable. — Improved Methods of Sounding. — The Cup-lead. — 

 Brooke's Sounding Instrument. — The ' Bull-dog ' ; Eitzgerald's ; 

 the ' Hydra.' — Sounding from the ' Porcupine.' — The Contour 

 of the Bed of the North Atlantic. 



In all deep-sea investigations it is of course of the 

 first importance to have a means of determining the 

 depth to the last degree of accuracy, and this is not 

 so easy a matter as might he at first supposed. 

 Depth is almost invariably ascertained by some 

 modification of the process of sounding. A weight 

 is attached to the end of a line graduated by attached 

 slips of different coloured buntine (the woollen mate- 

 rial of which flags are made, in which the colours are 

 particularly bright and fast) into fathoms, tens of 

 fathoms, and hundreds of fathoms ; or, for deep-sea 

 work, with white buntine at every 50, black leather 

 at every 100, and red buntine at every 1,000 fathoms. 

 The weight is run down as rapidly as possible, and 

 the number of fathoms out when the lead touches 

 the bottom gives a more or less close approximation 

 to the depth. 



