606 
ME. J. PEESTWICH ON STJBMAEINE TEMPEEATUEES. 
terranean ceased at a depth of 60 feet, and the annual variations at a depth of from 
1150 to 1300 feet. At this point Aime found a uniform temperature of 54° - 7, and 
was of opinion, from the observations of Berard, that no increase took place at greater 
depths. This degree he showed to be the average of the mean temperature between 
Toulon and Algiers, of the months of January, February, and March. 
In order to determine whether the decrease of temperature was gradual, or whether 
the instrument passed through warmer strata, Aime also used a thermometer which 
was let down upright and reversed at the bottom of the soundings. This he termed 
a “ thermometre a retournement.” Besides these, Aime employed the ordinary self- 
registering thermometer with an enlargement in one part of the tube to remedy the 
inconvenience of the quicksilver passing over the index. These several instruments 
were enclosed in copper cylinders strong enough to resist the pressure to which they were 
subjected. For moderate depths he preferred a glass tube hermetically sealed * * * § . 
In 1845 Captain (now Admiral) Spratt made 15 observations f from the surface to 
a depth of 1260 feet, in the Grecian archipelago, and obtained results in perfect 
accordance with those of Saussure and Aime in the Western Mediterranean. He 
afterwards made a more extended series of observations (34 in all) and to greater depths 
(7440 feet) in the eastern basin of the Mediterranean from Malta to Egypt J. Admiral 
Spratt at first used Six’s thermometer ; but finding that the index often moved, he 
resorted, in shallow seas of the archipelago, to the plan of taking the temperature of the 
mud brought up from the bottom by means of a sound formed of iron tubing. This plan, 
Admiral Spratt considered, gave more reliable results than the other. In every case in 
Forbes’s Yll.th zone, or between 1080 and 1200 feet, the mud indicated a temperature 
of 55°*5 ; and he concluded that there was no reason to suppose the temperature to be 
lower than 55° at any depth under 1800 feet. In the deeper waters he reverted to the 
use of Six’s thermometer. 
Captain (now Admiral Sir Edward) Belcher gives a series of eight observations he 
made in mid-Atlantic when crossing the equator in 1843, at depths of from 1800 to 
6000 feet§. Sir Edward informs me that a much larger number were made, but that 
they were not published at the time and have been unfortunately lost, with the exception 
of the few others recorded by Sir James Ross||. Sir Edward Belcher also mentions 
that he had a water-bottle of great strength, with two enclosed thermometers specially 
made by Carey, and that these instruments “ were tested continuously between 1835 
and 1846, and never found to vary from each other or from the standard which I 
[Sir E. B.] now possess, and which belonged to the Old Board of Longitude. They 
* Eor a description of his instruments see op. cit. Ann. Chim. et Phys. pp. 6-12. 
f Phil. Mag. for 1848, p. 169. 
± The Nautical Magazine for 1862, p. 9. Admiral Spkatt has also obligingly communicated to me the 
twenty-two unpublished observations to which is attached “ u ” in the Tables. 
§ Narrative of the Yoyage of H.M.S. ‘ Samarang’ during the years 1843-46. London, 1848, vol. i. p. 9. 
|| Antarctic Yoyage, vol. ii. p. 53. 
