ME. J. PEESTWICH ON SUBMAEINE TEMPEEATUEES. 
601 
Beeard, in 1831-32*, made another series of observations in the Mediterranean, and 
ascertained that the temperature of about 55°, noted by Saussure and D’Urville at 
depths of from 1000 to 3000, prevailed to the depth of 6400 feet. 
I cannot ascertain precisely when protection against pressure on the thermometer was 
first used. Parrot and LENzf made experiments on the effects of compression on 
thermometers in 1832, and found that in ordinary instruments they were excessive ; but 
this did not apply to Six’s self-registering thermometer, which from its form of con- 
struction offers much greater resistance to compression. 
It seems to me, however, that some form of protection must have been adopted by 
the French several years earlier. It is true that D’Urville merely says that he was 
provided with two of Bunten’s instruments, and makes no mention of the mode in 
which they were used ; but on comparing his observations in the Mediterranean, where 
the bathymetrical isotherms are at nearly constant levels, I find his results in such close 
agreement with those of Aime, obtained with protected instruments, and so free from 
variation dependent on depth alone, that I can only conclude that D’Urville’s thermo- 
meters were likewise protected. In the same way I infer that Berard also used similar 
instruments J. Thus their respective readings give : — 
1826. 
D’Frvilie. 
Soundings fl062 ft. 54°*2 Fahr. 
in the 1594 „ 54°-7 „ 
Mediterranean. L3189 „ 54 0, 7 „ 
1831. 1840. 
Berard. Aime. 
3189 ft. 55°*4 Fahr. 1148 ft. 54°-6 Faiir. 
3829 „ 55°-7 „ 
6377 „ 55°-4 „ 
For this reason I think it not improbable that the ocean observations of D’Urville 
were made with the same precautions, and need little or no correction. 
In 1839 Captain Wauchope§ recorded two more experiments made by him in 1836 
in tropical regions at depths of 1800 and 3918 feet, showing respectively temperatures 
of 52° and 43°. He also surmised that at a certain depth there might be a uniform 
temperature of about 40° in all seas. 
But the most remarkable voyage [| of the period was that of Captain Abel Du Petit- 
Thouars between 1836 and 1839. This expedition sailed from Brest in December 1836, 
touched at Teneriffe, Kio Janeiro, sailed round Cape Horn along the South- American 
coast, thence to the Sandwich Islands, and back by New Zealand, Bourbon, and the 
Cape. Fifty-nine observations were made ; but eleven failed owing to accidents with 
* Berard’s observations are taken from Aimk’s paper quoted further on. 
t Experiences de forte compression sur divers corps. Mem. Acad. Sci. St. Petersbourg, vol. ii. p. 595. 
E. Marcet and De ea Eive (Bibl. Univ. xxii. 1823, p. 265) had before this shown the influence of atmospheric 
pressure on the bulb of thermometers. 
t On the ‘ Porcupine’ expedition of 1869 a uniform temperature was noted of 54°-7 to 55 0, 5 in this area 
of the Mediterranean at and below a depth of 1000 to 1100 feet. (Proc. Boy. Soc. 1870, vol. xix. p. 221.) 
. § Edinburgh New Phil. Journ. vol. xxvi. 1838-39, p. 399. 
II Voyage autour du Monde sur la Fregate ‘ La Yenus,’ Capitaine Du Petit-Thouars. Paris, 1844. Physique, 
par M. nE Tessan, vol. ix. Tables, p. 385. 
