on Svhterranean Temperature. 9S5 



renheit the temperature of a mass of air equal to that which fil- 

 led the whole of the galleries. 



At the upper sta^e, the temperature of the air taken in the 

 waggon-way, at an equal distance from the sides, the ball of 

 the thermometer being suspended at a height of one foot from 

 the rock forming the roof, was as follows : 69°.3 Fahrenheit 

 near the shaft ; 72° Fahrenheit, a hundred and forty metres 

 farther on, that is to say, near a shaft forming a communica- 

 tion for ventilation between the two stages; and 73°.8 Fah- 

 renheit at the extremity of the gallery, that is to say, at a dis- 

 tance of 790 feet from the shaft. Proceeding in the same man- 

 ner, I found at the extremity of several galleries, whether paral- 

 lel or cross, a temperature varying from 73° to 73°.8 Fahren- 

 heit. The workmen, besides, had not entered the galleries for 

 some time ; the air was perfectly stagnant, at least to appear- 

 ance ; and, according to the commonly received ideas, their tem- 

 perature seemed calculated to give that of the surrounding rock. 



At the lower stage, proceeding in the same manner as above, 

 I found that the air at the bottom of the principal waggon- 

 way, that is to say 920 feet from the .shaft, marked 74°. 1 

 Fahrenheit. At the extremities of the other galleries into which 

 I entered, the temperature was only from four to five tenths 

 lower than the above. At the roof of the canal ending in the 

 ventilating chimney, the ascending air was 73°.6 Fahrenheit, 

 and consequently issued with a temperature more than 14° 

 Fahrenheit, above the external air. 



Lastly, having determined in a direct manner, which I con- 

 sider as accurate, and of which I shall give a description after- 

 wards, the proper and original temperature of the rock which 

 surrounded the bottom of the lower waggon-way, I found 

 it 62°.8. Thus I would have committed an error of nearly 11° 

 too high, had I, in imitation of most observers, given the tem- 

 perature of the air of the unfrequented galleries of the lower 

 stage of the Ravin mine, as representing the real temperature 

 of the zone of rock, which is situated in the same horizontal 

 plane. 



The example which I have just adduced, is so striking that 

 I believe it useless to relate the numerous facts of the same na- 

 ture, which I have collected at Littry and Decise. 



