502 LIFE IN THE DEEP SEA. 



and perhaps one or two other officers besides the one on duty, 

 awaited the arrival of the net on the dredging bridge ; and as 

 the same tedious animals kept appearing from the depths in all 

 parts of the world, the ardour of the scientific staff even abated 

 somewhat, and on some occasions the members were not all 

 present at the critical moment, especially when this occurred in 

 the middle of dinner-time, as it had an unfortunate propensity 

 of doing. It is possible even for a naturalist to get weary of 

 deep-sea dredging. Sir Wyville Thomson's enthusiasm never 

 flagged, and I do not think he ever missed the arrival of the 

 net at the surface. 



Often when the dredge or trawl appeared there was nothing 

 in it at all, and then frequently a somewhat warm debate ensued 

 between the members of the scientific staff and the naval 

 officers as to whether the instrument had ever been on the 

 bottom or no, the scientific view being that it had not. 



Sometimes there would be only a bright red Shrimp in the 

 net ; and this fact, on the one side, would be held as proof that 

 the bottom had been reached, whilst, on the other, it was main- 

 tained that the .Shrimp probably inhabited a region lying at 

 some distance above the bottom. The sledge irons of the 

 trawl-net were carefully examined as evidence in the matter, to 

 test whether they had been polished by friction on the bottom 

 or no, or whether they had any mud adhering to them. In 

 future dredging operations, it would be well to have a small 

 cup with a valve to it attached to the dredge or trawl, so that 

 it shall always retain a little of the bottom, and prevent the 

 possibility of the occurrence of such doubts. 



The conditions under which life exists in the deep sea are 

 very remarkable. The pressure exerted by the water at great 

 depths is enormous, and almost beyond comprehension. It 

 amounts roughly to a ton weight on the square inch for every 

 i,ooo fathoms of depth, so that at the depth of 2,500 fathoms 

 there is a pressure of two tons and a half per square inch 

 of surface, which may be contrasted with the 15 pounds per 

 square inch pressure to which we are accustomed at the level 

 of the sea surface. 



An experiment made by Mr. Buchanan enabled us to realise 

 the vastness of the deep-sea pressure more fully than any other 

 facts. Mr. Buchanan hermetically sealed up at both ends a 

 thick glass tube full of air, several inches in length. He 

 wrapped this sealed tube in flannel, and placed it, so wrapped 

 up, in a wide copper tube, which was one of those used to 

 protect the deep-sea thermometers when sent down with the 

 sounding apparatus. 



This copper tube was closed by a lid fitting loosely, and with 



