chap, v.] DEEP-SEA SOUNDING. 221 



every occasion, even at the greatest depths, he felt 

 distinctly the shock of the arrest of the weight upon 

 the bottom communicated to his hand. A careful 

 sounding was always taken immediately before letting 

 go the dredge. I will take as an example the sound- 

 ing which determined the depth of the deepest haul 

 of the dredge yet made, in 2,435 fathoms in the Bay 

 of Biscay on the 22nd of July, 1869, and describe 

 the modus operandi. 



The ' Porcupine ' was provided at Woolwich with 

 an admirable double cylinder donkey-engine of 12- 

 horse power (nominal), placed on the deck amidships, 

 with a couple of surging drums. This little engine 

 was the comfort of our lives ; nothing could exceed 

 the steadiness of its working and the ease with which 

 its speed could be regulated. During the whole ex- 

 pedition it brought in with the ordinary drum, the 

 line, whether sounding-line or dredge-rope, with 

 almost any weight, at a uniform rate of a foot per 

 second. Once or twice it was over-strained, and then 

 we pitied the willing little thing panting like an over- 

 taxed horse ; and sometimes we put on a small drum 

 for very hard work, gaining thereby additional power 

 at some expense of speed. 



Two powerful derricks were rigged for sounding 

 and dredging operations, one over the stern and one 

 over the port bow. The bow derrick was the stronger, 

 and we usually found it the more convenient to 

 dredge from. Sounding was most frequently carried 

 on from the stern. Both derricks were provided with 

 accumulators, accessory pieces of apparatus which 

 we found of great value. The block through which 

 the sounding-line or dr edging-rope passed was not 



