2 THE VOYAGE OF H.M.S. CHALLENGER. 



The operations carried on in the Pokcupine in the Bay of Biscay in the year 1869 

 at extreme depths were merely slight modifications suited to the different conditions, of 

 the ordinary methods which had long been employed in shallower water ; and they 

 worked smoothly and well. When it afterwards became my duty to superintend the 

 more important arrangements for the scientific work on board the Challengek, although 



FlQ. 1. — Ball's Naturalist's Dredge. 



Fig. 2. — Dredge witli " hempen tangles.' 



many changes were suggested, I made it a principle to deviate as little as possible from 

 a plan of working which had been shown to be at all events practicable. During the 

 progress of our voyage many alterations — some of them, such as the use of wire for 

 sounding introduced by Sir William Thomson, and employed with such signal success by 

 Captain Belknap in the U.S. ship Tuscarora, and of wire-rope for dredging adopted by 

 Professor Agassiz, evidently decided improvements — were introduced elsewhere ; but as 



