Clifton College Scientific Society. 83 



by self-registering thermometers of a peculiar construction. In 

 ordinary thermometers the pressure of the water (amounting to 

 one ton per square inch for every 800 fathoms) compressed the 

 bulb, and caused the instrument to register too high. This 

 source of error was completely counteracted by surrounding the 

 ordinary bulb with a second, the intervening space being partly 

 filled with fluid. There was also attached to the sounding line 

 an apparatus for collecting specimens of the water at any desired 

 depth. These instruments, and the deep-sea sounding apparatus, 

 by which the exceedingly heavy weight used in sounding was 

 detached at the bottom, were described in detail. The dredging 

 was carried on by a dredge of the ordinary ' naturalists' ' form, made 

 very viuch heavier, the rope employed being the best Chatham 

 ' hawser laid ' 2^-inch rope, of which 3000 fathoms were kept in 

 coils for use on deck, and wound in when required by a donkey 

 engine.* Sounding and dredging had been carried on successfully 

 at all depths down to 2435 fathoms, this being as great a deptli 

 below the surface of the sea as the summit of Mount Blanc is 

 above it, and the pressure at this point exceeding three tons per 

 square inch. 



The speaker then stated some of the results which had been 

 obtained. 



It had been most conclusively demonstrated that the notion of 

 bathymetrical zones of animal life was entirely erroneous, and 

 that animal life of the highest invertebrate types existed at all 

 depths. The habitats of particular animals had been shown to 

 depend upon temperature, and not upon depth. The range of 

 geographical distribution of many species had been enormously 

 increased ; a vast number of new ones had been added to the list ; 

 and several species, hitherto supposed to have become extinct, had 

 been discovered alive. A discussion of the physical results, and 

 especially of the thermometric observations, would have occupied 

 a whole lecture ; but it was stated broadly, that the temperature 

 of the North Atlantic diminished with the depth, though not in 

 proportion to it ; and that there was reason to believe that the 

 source of the vast body of water at and below 36° Fah., which 

 occupied the lower part of the North Atlantic basin, was a sub- 

 marine polar current, and that an interchange of polar and 

 equatorial water took place by a movement near the surface from 



* An important addition to the dredge, suggested by Captain Calver, R.N., 

 who commanded H.M.S. Porcupine in the 1869 and 1870 expeditious, was found 

 extremely serviceable. Long projecting rods of iron were attached to the dredge 

 rope, at right angles to it, just above the dredge. To the ends of these, 

 bundles of spun-yarn were attached, which swept the bottom of the sea, and iu 

 the hempen tangles of which many animals were secured. 



