140 Trof. B'lschoff on the Temperature of 



for example, according to Boussingault, the mean temperature 

 of the valley of Mof^dnlena in the Cordilleras, situated at a 

 height of more than 600 feet, is the same as at Carthagena, on 

 the sea coast. On the other hand, geological peculiarities and 

 proximity to active volcanos do not affect the climate. Purace, 

 Pasto, and Cumbal, which are commanded by active volcanos, 

 have not a higher mean temperature than Bogota, Santa Rosa 

 de Osos, and Ptiramo de Herve, which repose on a perfectly 

 unvolcanic soil. 



This subject is treated at greater length in Chapters XVII, 

 and XVIII. 



Ch.4P. XVI. — The unequal potoer of conducting heat, possessed bi/ 

 different rocks, causes differences in. the progression of the increase 

 of temperature towards the centre of the earth. 



This seems to be particularly striking with respect to metal- 

 liferous lodes. Fox* observed in a mine in Cornwall, that 

 thermometers sunk into a metalliferous vein, stood in general 

 2°.25 higher than when placed in holes bored in the rock, par- 

 ticularly in granite. Tin veins usually shewed themselves 

 colder than those which yielded copper. The tin mines of 

 the Sauberg at Ehrenjriedcrsdorff also shew a remarkably 

 low temperature ; indeed, it is a prevailing opinion there that 

 stanniferous mountains are colder than others. At Ehrenfrie- 

 dersdorf, the correctness of this opinion could never be ques- 

 tioned, because, in many parts of the mine, ice is at all seasons 

 of the year to be found in considerable quantities. The low 

 temperature of Beinrichssohle, in the Altenberg district in the 

 Erzgebirge, was also supposed to be ascribable to the rocks of 

 tinstone.:J: It may, however, be questioned whether this phe- 

 nomenon be not a consequence of the dislocated state of the 

 rock, caused by the peculiar method in which it is worked. 



• Annal. de Chim. et de Phys. vol. xvi. p. 80. Fox remarks that at equal 

 depths, granite and other hard rocks are, in general, of lower temperature 

 than clay-slate and other soft and porous rocks. 



t Reich, p. 87 and 107- 



t Ibid. p. 87 and 107- 



