THE VOYAGE OP THE CHALLENGER. :> 29 



cut-up, and " choppy " waves of the Atlantic. In the Atlantic, on the voyage of the 

 Challenger from Teneriffe to St. Thomas, a pretty level bottom off the African coast gradually 

 deepened till it reached 3,125 fathoms (over three and a half miles), at about one-third of the 

 way across to the West Indies. If the Alps, Mont Blanc and all, were submerged at this spot, 

 there would still be more than half a mile of water above them ! Five hundred miles further 

 west there is a comparatively shallow part two miles or so deep which afterwards deepens to 

 three miles, and continues at the same depth nearly as far as the West Indies. 



A few words as to the work laid out for the Challenger) and how she did it. She is 

 a 2,000-ton corvette, of moderate steam-power, and was put into commission, with a 

 reduced complement of officers and men, Captain (now Sir) George S. Nares, later the 

 commander of the Arctic expedition, having complete charge and control. Her work 

 was to include soundings, thermometric and magnetic observations, dredgings and chemical 

 examinations of sea-water, the surveying of unsurveyed harbours and coasts, and the re- 

 surveying, where practicable, of partially surveyed coasts. The (civil) scientific corps, under 

 the charge of Professor Wyville Thomson, comprised three naturalists, a chemist and 

 physicist, and a photographer. The naturalists had their special rooms, the chemist his 

 laboratory, the photographer his " dark-room/'' and the surveyors their chart-room, to 

 make room for which all the guns were removed except two. On the upper deck was another 

 analysing-room, " devoted to mud, fish, birds, and vertebrates generally ; " a donkey-engine for 

 hauling in the sounding, dredging, and other lines, and a broad bridge amidships, from which 

 the officer for the day gave the necessary orders for the performance of the many duties con- 

 nected with their scientific labours. Thousands of fathoms of rope of all sizes, for dredging 

 and sounding ; tons of sounding- weights, from half to a whole hundredweight apiece ; dozens 

 of thermometers for deep-sea f/cmperatures, and gallons of methylated spirits for preserving 

 the specimens obtained, were carried on board. 



Steam-power is always very essential to deep-sea sounding. No trustworthy results can 

 be obtained from a ship under sail ; a perpendicular sounding is the one thing required, and, of 

 course, with steam the vessel can be kept head to the wind, regulating her speed so that she 

 remains nearly stationary. The sounding apparatus used needs some little description. A 

 block was fixed to the main-yard, from which depended the " accumulator," consisting of strong 

 india-rubber bands, each three-fourths of an inch in diameter arid three feet long, which ran 

 through circular discs of wood at either end. These are capable of stretching seventeen feet, 

 and their object is to prevent sudden strain on the lead-line from the inevitable jerks and 

 motion of the vessel. The sounding-rod used for great depths is, with its weights,* so 

 arranged that on touching bottom a spring releases a wire sling, and the weights slip off and 

 are left there. These rods were only employed when the depths were considered to be over 

 1,500 fathoms; for less depths a long, conical lead weight was used, with a "butterfly valve/' 

 or trap, at its basis for securing specimens from the ocean bed. There are several kinds of 

 " slip " water-bottles for securing samples of sea- water (and marine objects of small size 

 floating in it) at great depths. One of the most ingenious is a brass tube, two and a half feet 

 in length, fitted with easily-working stop-cocks at each end, connected by means of a rod, on 



* The " sinkers" wore usually allowed at the rate of 1121b. for each 1,000 fathoms. 



