an Subterranean Temperature. 283 



The heat produced by the lighting presents two cases, ac- 

 cording as oil or candles are employed. 



I compare the oil of the miners' lamps to linseed oil, in re- 

 gard to its manner of burning. Now, according to Count 

 llumford, the combustion of 1 ounce of linseedioil,;raises the tem- 

 perature of 1 ounce of water to 16°.28 Fahrenheit. Making use 

 of the same data as the above, we find that in one hour, the 

 presence of a lamp burning 15 grammes of oil (as at Carmeaux, 

 for example, where coarse walnut oil is employed), increases, by 

 1° Fahrenheit, the temperature of a mass of air of 26,000 cubic 

 feet, taken at an original temperature of 54° Fahrenheit. Thus 

 four of these lamps produce about as much heat as three work- 

 men. 



Count Rumford found, that the heat furnished by the com- 

 bustion of 1 ounce (gramme) of tallow, raised 1 ounce of water to 

 15.064° Fahrenheit ; whence it follows, that in one hour the 

 light obtained (as at Littry, where the candles are from twenty- 

 eight to thirty-two in the pound) by the consumption of 7^ 

 grammes ot candles, raises 1° 12,015 cubic feet of air, taken at 

 the original temperature of 54° Fahrenheit. 



According to these data, the presence of two hundred miners, 

 and two hundred lamps suitably distributed, would suffice to 

 raise 1° Fahrenheit in an hour, the temperature of a mass of air 

 equal to that which a gallery of 3 feet by 6 feet, and 656,900 

 feet (about 124 English miles) in length, would contain. It is 

 not without reason, therefore, that the presence of workmen and 

 lights has been alleged necessarily to exercise a great influence up- 

 on the temperature of the air of mines. In general this influence 

 tends, during the greater part of the year, to counterbalance more 

 or less completely the effect of causes which might keep the tempe- 

 rature of the air contained in an excavation, beneath the proper 

 temperature of the surrounding rock. Duringthe rest of the time 

 it augments the excess of the temperature of the air, over that of 

 the rock with which it is in contact at each stage. It acts, be- 

 sides, in the most variable manner, according to the number and 

 distribution of the lights and workmen, the capacity and depth 

 of the works, and the manner in which it combines with the two 

 first causes of disturbance which we have explained. There is 

 nothing more changeable than these combinations. There evi- 



