378 M. L. Cordier, Examination of recent Eccperiments 



son *, in the lead and silver mines of Poullaouen and Huelgoet 

 in Bretagrie. In Switzerland, we have the experiments made 

 about forty years ago by De Saussure -f, in the salt mines of Bex. 

 In Saxony, those of MM. Freiesleben and Humboldt |, collect- 

 ed in 1791 ; of M. Daubuisson ||, made in 1802; and especially 

 those of M. de Trebra, in 1805, 1806, 1807, and 1815 §. In 

 Great Britain, we have to mention numerous experiments made 

 from 1815 to the present day, by Mr Lean, Mr Rede, and especial- 

 ly Mr W. Fox, in the copper and lead mines of Cornwall and De- 

 vonshire ; and by Messrs Bald, Dunn, and Fenwick, in the coal 

 mines of the north of England ^. Lastly, we must also include 

 into the number those made by M. de Humboldt in several mines 

 in Peru and Mexico **. 



The number of mines in which these different observations have 

 been made is upwards of forty ; that of the individual markings 

 of temperature is about three hundred. 



Nearly two thirds of these markings of temperature have been 

 made from the air contained in subterranean cavities, and most 

 of the others from the water which presents itself in so many 

 ways in these cavities. A very few are from experiments made 

 with the view of directly determining the temperature of the rock 

 surrounding the excavations ; but several of these latter mark- 

 ings have the advantage of being mean temperatures taken from 

 a great number of sedentary observations. With regard to the 

 former, they all result from observations made on descending into 

 the mines for a short time. 



I take no notice of some less important observations which have 

 been made in the mines, quarries, and caves of various other coun- 

 tries, because they have been made singly and almost accidental- 

 ly. They refer, in general, to the temperature of the air of ca- 



• Journal des Mines, t. xxi. p. 119. 



-|- Voyages dans les Alpes, sect. 1088. 



X Annales de Chimie et de Physique, t. xiii. p. 210. 



II Description de Mines de Freyberg, tit. iii. pp. 151, 186, 200; Journal 

 des Mines, tit. xi. p. 517 ; and xiii. p. 113. 



§ Annalee des Mines, tit. i. p. 377, and tit. iii. p. 59. 

 ^ Annales de Chimie et de Physique, t. xiii, p. 200 ; t. xvi, p. 78 ; t. xix, 

 p. 438; t. xxi. p. 308; and Geogr. Distrib. of Plants, by N. J. Winch, p. 51. 

 *• Annales de Chimie et de Physique, t. xiii. p. 207. 



