HOW THE SEA-DEPTHS ARE EXPLORED. 269 



sel drifts gradually to leeward ; and, when the whole (say) 18,000 feet 

 of rope are out, C W and D might represent respectively the relative 

 positions of the vessel, the weight attached 3,000 feet from the dredge, 

 and the dredge itself. The vessel now steams slowly to windward, 

 occupying successively the positions E, F, G, H. The weight, to 

 which the water offers but little resistance, sinks from W to W, and 

 the dredge and bag sink more slowly from D to B. The vessel is now 

 allowed to drift back before the wind, from H toward C. The tension 

 of the motion of the vessel, instead of acting immediately on the 

 dredge, now drags forward the weight (W), so that the dredging is 

 carried on from the weight, and not directly from the vessel. The 

 dredge is thus quietly pulled along, with its lip scraping the bottom in 

 the attitude which it assumes from the centre of weight of its iron 

 frame and arms. If, on the other hand, the weights were hung close 

 to the dredge, and the dredge were dragged directly from the vessel, 

 owing to the great weight and spring of the rope, the arms would be 

 continually lifted up, and the lip of the dredge prevented from scrap- 

 ing. In very deep dredging this operation of stealing up to windward 

 until the dredge-rope is nearly perpendicular, after drifting for half an 

 hour or so to leeward, is usually repeated three or four times. 



" At 8.50 p. m. we began to haul in. The donkey-engine delivered 

 the rope at the rate of rather more than a foot per second without a 

 single check. A few minutes before one A. M. the weights appeared, 

 and, a little after one in the morning, eight hours after it was cast 

 over, the dredge was safely hauled on deck, having in the interval ac- 

 complished a journey of upward of eight statute miles. The dredge 

 contained 1^ cwt. of very characteristic pale-gray Atlantic ooze." The 

 total weight brought up by the engine was : 



"Weight of rope, reduced to in water . = 1,375 lbs. 



Dredge and bag, " " " = 275 " 



Ooze brought up, . = 168 " 



Weight attached ....... 224 " 



2,042 



As an abundant and characteristic invertebrate life is now shown 

 to exist at such great depths, it is inferred to extend to all depths ; 

 and thus the whole ocean-bed becomes in future the domain of the in- 

 quisitive naturalist. But, as Dr. Thomson remarks, little more can be 

 said, for his work is all before him : " A grand new field of inquiry has 

 been opened up, but its culture is terribly laborious. Every haul of 

 the dredge brings to light new and unfamiliar forms forms which 

 link themselves strangely with the inhabitants of past periods in the 

 earth's history ; but as yet we have not the data for generalizing the 

 deep-sea fauna, and speculating on its geological and biological rela- 

 tions ; for, notwithstanding all our strength and will, the area of the 

 bottom of the deep sea which has been fairly dredged may still be 

 reckoned by the square yard." 



