258 THE POPULAR SCIENCE MONTHLY. 



this experiment, that a second expedition was arranged in 1869, and 

 the government surveying-vessel Porcupine was assigned to the nat- 

 uralists to carry on the work. This expedition was also so highly 

 successfnl, that the ship Challenger has now started out on a four 

 years' voyage around the world to carry out a comprehensive plan of 

 deep-sea observations. We noticed very briefly last month the ad- 

 mirable work of Prof. Wyville Thomson on " The Depths of the Sea," 

 giving a history of what has been lately done in the investigation of 

 the subject. We propose now to lay Prof. Thomson's work under 

 contribution for the benefit of our readers, and especially to give some 

 account of the instruments of ocean-research, and the way the explora- 

 tion is conducted. 



It may be remarked, in passing, that, when the dredging of the 

 deep seas was found to be feasible, questions of large scientific interest 

 and moment, which had been hitherto regarded as inaccessible, were 

 suddenly brought within the range of practical solution. It was a 

 popular opinion, shared also by men of science, that the bottom of the 

 sea was a dark and desolate waste, subject to such tremendous press- 

 ure as to render all life impossible. Prof. Thomson observes : " The 

 enormous pressure at these great depths seemed at first sight alone suffi- 

 cient to put any idea of life out of the question. There was a curious 

 popular notion, in which I well remember sharing when a boy, that, in 

 going down, the sea-water became gradually under the pressure heavier 

 and heavier, and that all the loose things in the sea floated at different 

 levels, according to their specific weight : skeletons of men, anchors, 

 and shot, and cannon, and, last of all, the broad gold-pieces lost in the 

 wreck of many a galleon on the Spanish Main, the whole forming a 

 kind of false bottom to the ocean, beneath which there lay all the 

 depth of clear, still water, which was heavier than molten gold. The 

 conditions of pressure are certainly very extraordinary. At 12,000 

 feet a man would bear upon his body a weight equal to 20 locomotive- 

 engines, each with a long goods-train loaded with pig-iron. We are 

 apt to forget, however, that water is almost imcompressible, and that, 

 therefore, the density of sea-water at a depth of 12,000 feet is scarcely 

 appreciably increased." 



Contrary to all anticipation, it was found that highly-organized 

 representatives of all the invertebrate classes do live under these con- 

 ditions of enormous pressure. The bottom of the ocean is, therefore, 

 to be regarded as habitable, and is proved to be actually inhabited by 

 numberless forms of animal life. A new world was thus opened to 

 the naturalist, which, although difficult of access, was yet accessible 

 and must be investigated. The pioneers in the exploration of course 

 encountered very formidable obstacles ; but the field was too vast 

 and the promise too rich to be neglected, and how it was regarded by 

 the devotees of research may be gathered from the following words of 

 Dr. Thomson : 



