Report of the Voyage of the Coquille. 203 
therefore reduced in the ratio of the attenuated atmosphere. 
This density would be modified too by its saline contents. 
4. The depth to which the ball of the thermometer is plunged 
in the water, and the place it occupies in the cylinder. 
5. The evolving steam or heated vapour will also affect the 
stem of the instrument, and with it disturb the results. 
6. The form, size, and material of the vessel will also con- 
tribute their share in modifying the indication. 
7. The depth of the vessel containing the boiling water. 
8. If made in the house, the difference between the internal 
and external temperature will be a modification of the phe- 
nomena. 
9. A gust of wind, wafted from the glacier, avalanche, or 
other cooling surface, will disturb and change the density of 
the incumbent air; and therefore irregularities such as these 
must be provided for. 
10. The greater or less rapid escape of the steam will ne- 
cessarily render capricious the observed temperature. 
11. The period of the day or night, strength of the sun- 
beams, &c.—all concur in varying the results. 
It will, I apprehend, be very difficult to maintain a success- 
ful struggle against all these combining ‘circumstances; and 
they thus render this instrument, certainly ingeniously applied 
by Mr. Wollaston, nearly useless for considerable elevations. 
Captain Hall’s experiments corroborate the inference; and at 
those he made at the village of Simpoln on the Simplon, (with 
an instrument constructed under the immediate sanction of 
Mr. Wollaston,) in 1818, I had the satisfaction and pleasure 
of being present. 
January 27, 1826. J. Murray. 
XXXII. Report made to the Academy of Sciences, 22d of 
August 1825, on the Voyage of Discovery, performed in the 
Years 1822, 1823, 1824, and 1825, under the command of 
M. Dourrrrey, Lieutenant of the Navy*. 
(Commissioners: MM. pr Humsotocrt, Cuvier, DESFONTAINES, 
CorpiER, LATREILLE, DE RosseL; and Araco, Reporter.) 
GINCE the return of peace, many voyages have been per- 
formed for the advancement of the sciences and of naviga- 
tion. Captain Gauttier’s maps of the Mediterranean and of 
the Black Sea; Captain Roussin’s labours on the coasts of 
Africa and of Brazil; the expedition of Captain Freycinet ; the 
hydrographic operations directed by our colleague Beau- 
tems-Beaupré, will be durable monuments of the enlightened 
* From the Annales de Chimie, tom. xxx. p. 397. : 
2C2 protection 
