II THE PROBLEMS OF THE DEEP SEA 41 



to prevent it from pulling the dredge directly 

 upwards, and is then made fast while the boat 

 goes ahead. The dredge is thus dragged along 

 and scrapes oysters and other sea-animals and 

 plants, stones, and mud into the bag. When the 

 dredger judges it to be full he hauls it up, picks 

 out the oysters, throws the rest overboard, and 

 begins again. 



Dredging in shallow water, say ten to twenty 

 fathoms, is an easy operation enough ; but the 

 deeper the dredger goes, the heavier must be his 

 vessel, and the stouter his tackle, while the opera- 

 tion of hauling up becomes more and more 

 laborious. Dredging in 150 fathoms is very hard 

 work, if it has to be carried on by manual labour ; 

 but by the use of the donkey-engine to supply 

 power, 1 and of the contrivances known as " accumu-, 

 lators," to diminish the risk of snapping the dredge 

 rope by the rolling and pitching of the vessel, the 

 dredge has been worked deeper and deeper, until 

 at last, on the 22nd of July, 1869, H.M.S. Porcupine 

 being in the Bay of Biscay, Captain Calver, her 

 commander, performed the unprecedented feat of 

 dredging in 2,435 fathoms, or 14,610 feet, a depth 



1 The emotional side of the scientific nature has its singulari- 

 ties. Many persons will call to mind a certain philosopher's 

 tenderness over his watch "the little creature" which was 

 so singularly lost and found again. But Dr. Wyville Thomson 

 surpasses the owner of the watch in his loving-kindness towards 

 a donkey-engine. "This little engine was the comfort of our 

 lives. Once or twice it was overstrained, and then we pi tied the 

 willing little thing, panting like an overtaxed horse. " 



