TEMPEEATUEE OF THE DEEP SEA. 635 



TEMPERATURE. — In recent times a great amount of attention has 

 been given to the subject of the Temperature of the Waters of the Ocean, 

 from the surface to the bottom, as affording a clue to the system of its 

 circulation. Allusion has already been made to this in (247) page 298, 

 and in (362) page 377. In the earlier experiments, all enquiries into 

 deep-sea Temperatures appear to have been alike deceptive and unsatis- 

 factory, as the indications obtained, even by the most careful observers, 

 with the best of instruments, were utterly at variance with any theory 

 that could associate Temperature as a leading cause of the circulation of 

 the waters of the Ocean. Thus, temperatures that reason would expect 

 to find — say 30° F. — at great depths, were made to appear to be 42° or 43°, 

 the disparity being less as the depth diminished.* This was caused by 

 the elasticity of the glass bulbs yielding to the pressure of the water, 

 though they recovered their normal condition on reaching the surface, so 

 that the effect of this pressure remained unknown. 



Protected bulbs for Deep-Sea Thermometers had been devised by 

 Admiral FitzEoy, and used by Capt. PuUen in the Atlantic and Indian 

 Oceans, but the principle was forgotten until revived and carried out 

 again, as related by Dr. J. J. Wild, in " Thalassa," pages 31 — 34. He 

 says : — " The want of an eflficient deep-sea thermometer, which more or 

 less vitiates all the observations of earlier explorers, was especially ex- 

 perienced during the cruise of H.M.S. Lightning in 1868, the first 

 expedition fitted out for sounding and dredging purposes by the joint co- 

 operation of the Eoyal Society and the English Admiralty. Of the 

 thermometers used on this occasion, several returned to the surface broken 

 by the pressure to which they had been exposed, and the indications 

 given by the rest varied so much as to render the discovery of a ther- 

 mometer free from this error a matter of paramount importance for the 

 success of future deep-sea exploration. By a happy coincidence, the 

 desired improvement was effected at the moment when a second expedi- 

 tion was being prepared. 



" In April, 1869, previous to the departure of H.M.S. Porcupine on her 

 first cruise, at a meeting of the Deep-Sea Committee of the Eoyal Society 

 of London, Dr. W. A. Miller suggested a simple expedient for protecting 



• Mr. Prestwich collected these series of observations, as they form a valuable supple- 

 ment to those collected since 1868. See " Tables of Temperatures of the Sea at Various 

 Depths below the Surface, taken between 1749 and 1868, collated and reduced, with 

 notes and sections," by Joseph Prestwich, F.R.S., F.G.S., in the " Proceedings of the 

 Royal Society," No. 154, 1874. 



Much recent information on this subject is given in the works mentioned in the note 

 on page 916, and the following have also been referred to, in dealing with this section. 

 The " Wind and Current Charts " issued by the Meteorological Office, in 1872, and 

 referred to on page 294, &c., and " Charts showing the Surface Temperature of the 

 Oceans," issued in 1884 ; '' Further Enquiries on Oceanic Circulation," in the " Pro- 

 ceedings of the Royal Geographical Society," vol. xviii, 1874, and a Paper " On the 

 Temperature of the Deep-Sea Bottom," in the " Proceedings," vol. xxi, 1877, both by 

 Dr. Wm. B. Carpenter, F.R.S. ; and " Wissenschaftliche Ergebnisse einer Forschungs- 

 reise zur Zee, in 1891 und 1892," by Dr. G. Schott, in " Erganzuugshef t No. 109 zu 

 Petermann's Mitteilungen," 1893, which contains a great deal of iiiterestiiig matter 

 concer]\ing Temperature, Specific Gravity, Currents, <i:c. 



