Prof. W. Thomson on the Depths of the Sea. 115 



about 300 fathoms, it altogether ceased. Forbcs's experience 

 was much wider than that of any other naturalist of his time ; 

 the practical difficulties in the way of testing his conclusions 

 were great, and they were accepted generally by naturalists 

 without question. There was, besides, a popular impression 

 that the conditions a mile beneath the surface of the sea must 

 be so very peculiar as to make it difficult to conceive that ani- 

 mals, more or less nearly related to forms inhabiting the upper 

 world, coidd exist there ; accordingly no attempt was made to 

 dredge at great depths, except on the Scandinavian coast ; 

 and the results of the scattered observations made there have 

 only appeared within the last few years. Except in one or 

 two cases Avhich never became very generally knoAvn, all the 

 few creatures which came up to protest against Forbes's theory 

 came clinging to sounding-lines, and were valueless for abso- 

 lute proof, as their mode of capture constantly involved the 

 question, which at that time we were unable to answer, whe- 

 ther there might not be pelagic forms of the groups to which 

 they belonged. 



In the year 1860, H.M.S. ^ Bulldog' sounded over the At- 

 lantic plateau ; and shortly after her return, Dr. Wallich, the 

 surgeon-natm*alist who accompanied her, published a warm 

 and able defence of the bottom of the sea as an inhabited re- 

 gion. The evidence of the existence of highly organized 

 forms at great depths was not even yet, however, quite con- 

 clusive, as it still depended on starfishes clinging to lead-lines ; 

 and although, from want of data, the subject was little dis- 

 cussed, the feeling of naturalists seemed still to be in favour 

 of Forbes's " zero of animal life." 



The Cruise of the ' Lightning.'' — About the time of Sars's 

 explorations in Lofoden, my friend Dr. Carpenter and I 

 were engaged in some investigations which, made the dis- 

 covery of Rhizocrinus especially interesting to us ; and we 

 talked over, again and again, the curious questions, both 

 geological and biological, which Sars's dredgings suggested. 

 We finally arranged that I should write a letter to Dr. Car- 

 penter, who was then Vice-President of the Royal Society, 

 sketching out what I conceived to be a promising line of 

 inquiry, indicating generally the results which I anticipated, 

 and urging him to endeavour to induce the Council of the 

 Royal Society to apply to the Admiralty for a vessel fitted 

 with dredging-gear, that, among other questions, tlic question 

 of deep-sea life might, if possible, be settled definitely, by 

 bringing up a quantity of the bottom, with its inhabitants, if 

 there were any, along with it. The Council of the Royal 

 Society acceded to Dr. Carpenter's request; and the Admiralty 



