380 Prof. BischofF on tlie Temperature q/' 



found a constant temperature of 43°.04. In lesser depths than 

 forty fathoms, the temperature varies according to circumstances, 

 but to that hmit it always decreases from the surface downwards. 

 In the Lake of Thun, De la Beche found the temperature at 

 the surface to be 59°.9, whilst at a depth of 106 fathoms it was 

 41°.4 ; and in the LaJce of Zug the temperature on the surface 

 was 58°, whilst at a depth of thirty-eight fathoms it was 41°. 

 Three hundred to four hundred fathoms deep in iheLagodi Como, 

 Volta found a temperature of 43°.2.* On the 16th April 1798, 

 Von Humboldt found the temperature of the water of the Lake 

 of Barthomew, in the Berchtesgaden Alps, at a depth of 2 feet, 

 to be 45°.83; at 42 feet, 43°.13; ai 60 feet, 41°; and at an- 

 other spot, at a depth of 84 feet, 42°.09.t Recent measure- 

 ments of D'UrvillejJ and of Boubee in the Lake of Oo, near 

 Bagneres de la Chou,§ have given the same results. 



Thus we find that the temperature in the depths of lakes ap- 

 proaches that of fresh water at its greatest density, which, ac- 

 cording to the latest accurate experiments of Stampfer, is 38°.7. || 



On the temperature of the sea in various depths, numerous 

 observations have been made, sometimes giving contradictory 

 results, which may have been partly owing to the various me- 

 thods and instruments used. 



From more than fifty observations, made by Castberg ^ on 

 the temperature of the water, at depths varying up to 200 feet 

 on the coast of the Mediterranean, he found no regular varia- 

 tions. Peron** concludes from his own observations, as well as 

 from those of Irvine and Forster, 1*^, That far from the coast, 

 the temperature of the sea is lower at all depths than at the sur- 

 face, and that it decreases with the depth, apparently according 

 to a certain law ; 2d, That this holds good, as well for the 

 frozen seas of the polar regions, as for the burning climates un- 



* Gilbert's Annal. vol. ii. p. 402. 



t Reise in die Acquin. Gegend. iii. 132. t Bibl. Univ. 1833, Nov. 323. 



§ London and Edinb. Phil. Mag. 1832, p. 383. 



II JahrbUcher des K. K. Polytechnischen Instituts zu Wien, vol. xvi. p. 48. 

 ^ Gilbert's Annal. vol. xix. p. 344. 



*• Annates du IMuseuni d'Hist. Nat. t. v. p. 123 to 148, and .Tourn. de 

 I'hys. t. lix. ]). 301. Also in Gilbert's Annalen, vol. xix. p. 427. 



