602 
ME. J. PEESTWICH ON SUBMAEINE TEMPEEATUEES. 
the instruments, and twenty gave wrong readings owing to the great pressure forcing 
water into the cylinder. Amongst the successful observations, two at a depth of 6600 
feet in the Pacific, and of 6000 feet off the Cape, recorded temperatures of 36 0, 1 and 
37 0, 4 ; a third in the North Atlantic, lat. 4 0, 23 and 6406 feet deep, gave 37°*8 F. ; while 
another, at a depth of 12,271 feet near the equator in the Pacific (on which occasion 
the cylinder was crushed by the pressure and the instrument broken, and the index 
jammed and fixed), gave a reading of 34°*8 or 35°Fahr. 
This was the first voyage in which precautions against pressure were systematically 
and professedly taken ; instruments of special construction were provided. The form 
adopted was Six’s thermometer, modified by Bunten, of Paris. They were enclosed 
in strong brass cylinders* to protect them from pressure, and they were always left down 
for half an hour. After the return of the expedition the thermometers were tried with 
a standard instrument, and found to have a reading only yu to of a degree Cent, 
higher than on starting. It was found, however, that the cylinder would not bear a 
pressure of more than about 12,000 feet; and that at all depths it was occasionally 
filled with water. In these latter cases Du Petit-Thouars used a correction of which 
we shall speak presently, and gives the corrected with the uncorrected reading. 
Corrections were also made for the angle the rope took with the vertical. There is 
therefore every reason to suppose that the deep-sea temperatures obtained on this 
voyage may be accepted as perfectly reliable. 
The ‘ Bonite,’ under the command of Captain V a tel ant f, was also despatched from 
France in 1836 to the Indian Ocean, Chinese seas, and the Pacific. Sixteen obser- 
vations in the Atlantic and Indian Oceans are recorded at depths of from 244 to 
8838 feet. The ‘ Bonite ’ was likewise provided with Bunten’s thermometers. They 
were wrapped in wool and placed in a glass tube, which again was enclosed in a copper 
cylinder closed by a screw at each end, and left down 18 to 20 minutes. In the first 
deep sounding (700 brasses) recorded the cylinder is stated to have come up full of 
water. This throws doubt on all the subsequent experiments ; and as no reference at 
all is made to the state of the cylinder in the other soundings, and the readings are 
more concordant with the “full cylinder” ones of Du Petit-Thouars, I think a 
correction should be applied to all his deeper observations. A large number of surface- 
temperatures were taken, and it was remarked again that in the Pacific the sea is more 
frequently warmer than the air, except under the equator. 
Another voyage J of research was undertaken by France in 1838 to the Arctic seas, 
* Du Petit-Thouars gives no particulars of the construction of his instruments ; but Arago, in his report 
of the results obtained on this voyage, speaks of the “ therm ometrographe de M. Punter enferme dans un etui 
cylindrique en laiton de 33-4 mill, de diametre interieur et de 15 - 6 mill, d’epaisseur,” which I presume refers 
to Du Petit-Thouars’s instruments. — Comptes Eendus, 1840, vol. xi. p. 311. 
t Yoyage autour du Monde sur la Corvette ‘ La Bonite,’ Capitaine Yaillant. Geol. et Miner, par M. Che- 
vxlier, pp. 232, 390-1 ; and Physique, par. M. Darondeau, ‘ Observations Meteorologiques.’ 
t Y oyage en Scandinavie et au Spitzberg de la Corvette ‘ La Eecherche.’ Geographie et Physique, vol. ii. p. 279. 
