600 
ME. J. PEESTWICH ON STJBMAEINE TEMPEEATUEES. 
In 1825 an important expedition*, under the command of Captain Beechey, was 
despatched by the Government round Cape Horn to the Pacific Ocean and Behring 
Strait. Aided by Mr. Collie, the Surgeon, a large and valuable series of meteorolo- 
gical observations were made, including ninety-seven single and serial experiments on 
deep-sea temperatures in the North and South Atlantic and North and South Pacific, 
ranging from lat. 56° S. to 70° N., and at depths from 30 to 5124 feet. These were 
arranged in Tables according to latitude for each ocean. No very low temperatures are 
recorded, but the decrease with the depth is persistent, Six’s thermometers were used, 
but no particulars are given of how they were used f . 
The great voyage of Admiral FitzRoy from 1826 to 1836, productive as it was of such 
valuable results in other branches of science, added little to our knowledge of deep-sea 
physics. Only two sets of observations, both serial, were made in the Indian Ocean at 
depths of from 30 to 2500 feetj. Six’s thermometers are mentioned, but without any 
other, particulars. 
In 1826-29 also another important surveying and exploring expedition § proceeded 
from France under the command of Captain Dumont D’Urville, aided by a staff of 
scientific officers. He was instructed by Arago to pay particular attention to deep-sea 
soundings and temperatures, and informed of the precautions essential in making such 
observations. D’Urville proceeded from Toulon through the Straits of Gibraltar to 
Teneriffe, across the Indian Ocean to Australia, New Zealand, the Eastern Archipelago, 
and back by the Mauritius, the Cape, and Ascension, making observations in all the seas 
he traversed, at depths varying from 50 to 6160 feet, and to the number altogether of 66, 
the lowest temperature recorded being 40°. These he tabulated according to zones of 
depth ; and he incorporated also in his Tables the experiments of all preceding observers, 
beginning with Cook and Forster. D’Urville concluded from his observations that 
in the open ocean the temperature at and below 3198 feet (600 brasses) is nearly constant 
between 39° and 41° — that it might be perhaps 40° Fahr. He also supposed that a belt 
of this uniform temperature existed between the latitudes of 40° and 60°. D’Urville 
was evidently led to this hypothesis of a zone of uniform temperature from assuming 
the greatest density of sea-water to be, as with fresh water, between 39° and 40°. His 
observations in the Mediterranean confirmed those of Saussure, viz. that the w r aters 
of that sea, below the depth of 1000 feet, had a uniform temperature of about 55°. 
In 1828 Graah made a few observations in the North Atlantic ||, but no particulars 
are given of the instruments he used. 
* Narrative of a Yojage to the Pacific and Behring Strait in H.M.S. ‘Blossom’ in 1825-28. London, 
1831. Appendix, Table X. p. 731. 
t Sir Edward Belcher, however, tells me that Captain Beechey’s thermometers “ were enclosed in copper 
cases with tow above and below,” and that no protection against pressure was employed. 
X Narrative of the Surveying Yoyage of H.M.S. ‘ Adventure ’ and ‘ Beagle.’ Appendix to vol. ii. p. 301. 
§ Yoyage de l’Astrolabe, vol. v. of Meteorologie, Physique, et Hydrographie. Paris, 1833. Chapter III. 
Physique, pp. 51*-85*. 
|| Narrative of an Expedition to the East Coast of Greenland. London, 1837, p. 21. 
