382 Prof. BischofF on the Temperature of 



wells of Amsterdam, which are sufficiently deep, a temperature 

 sensibly lower than the mean temperature at the surface ? Yet, 

 notwithstanding the remarks communicated by Von Buch al- 

 ready thirty years ago, Parrot has lately again attempted to 

 bring forward the decrease of temperature of the sea, and of 

 lakes, in proportion to the depth, as an objection to the increase 

 of temperature towards the centre of the earth* But this ob- 

 jection has been silenced by Kloden.t 



The decrease of temperature in the sea, in proportion to the 

 depth, has also been confirmed by Captains Ross and Sabine, 

 as well as for the northern ocean by Lieutenant Parry.;]; On 

 the other hand, Lieutenant Franklin found the temperature sen- 

 sibly higher, in high latitudes, at great depths in the Greenland 

 Sea, than near the surface, and the difference was frequently as 

 much as 9°.00 or 11°.25. Other officers of this expedition, 

 Lieutenants Beechy and Fisher, observed the same. As most 

 of Franklin's observations were made whilst the ship was sur- 

 rounded with ice, the temperature of the surface of the sea must 

 have been about the freezing point, which was probably the 

 cause of his contradictory results. § These observations can, 

 therefore, not be taken into consideration in the comparison of 

 the temperature of the sea at its surface, and at various depths. 



We are indebted for a valuable series of observations on the 

 temperature of the sea at various depths, to an observer in whom 

 the utmost reliance may be placed, namely, the astronomer who 

 joined Krusenstern's Voyage of Discovery, the late Horner || of 

 Zuriich. He found that the temperature of the sea invariably 

 diminishes as the depth increases. But single spots are to be 

 found in the sea, where the temperature is greater in the depths 

 than at the surface. Hot springs and volcanic action may cause 

 considerable partial elevations of temperature in the sea, as, for 



• Von Leonhavcl und Bronn JahrbUcher der Mineralogie, Geognosie, Geo- 

 logic, &c. 1830, fasc. 3. p. 334. 



t Ibid. 1831, fasc. 4. p. 384. 



X Alex. Marcet's lecture before the Royal Society of London, 20th May 

 1819. 



§ See Gilbert's Annal. vol. xx. p. 254. 



II Ibidem, vol, Ixiii. p. 2C6, and following. 



