iii Hummari/ Itevieiv of the late Investigations 



leries by infiltration through the porous lode. The gases ex- 

 tricated from the exploded gunpowder being of superior gra- 

 vity to ail", may, in like manner, be safely considered as car- 

 riers of temperature to the inferior parts of the mine. Of the 

 actual power of all these various sources in raising the tem- 

 perature of mines, I shall now proceed to make moie parti- 

 cular inquiry." 



From the experiments of Count Rumford and Mr. Dalton, 

 Dr. Forbes estimates, that one pound of tallow, during com- 

 bustion, will produce an elevation of 1° in the temperature of 

 1872 gallons of water. He considers the wlioU^ produce of 

 heat from the explosion of gunpowder to be equal to that re- 

 sulting from the combustion of an equal weiglit of charcoal, 

 and thus, reasonmg from the experiments of Crawford and 

 Dalton, that the explosion of one pound of gunpowder will 

 raise 980 gallons of water 1°. With regard to the operation 

 of friction and percussion in raising the temperature of mines. 

 Dr. F., " without taking any notice of the effect of the friction 

 of the pumps, rods, 8:c., the incessant operation of rending 

 the lode and rock by the pick-axe and lever," only considers 

 " the probable influence of boring the rock for the reception 



of the gunpowder for blasting." "What may be the 



precise amount of heat evolved by this operation," he says 

 after a preparatory estimate, " I am at present quite unpre- 

 pared to say ; nor am I sui'e that I can foim a conjecture re- 

 specting it at all approximating to the truth. I should, how- 

 ever, be disposed to consider the action of four borers con- 

 tinued for 24 hours, as equal to the effect of the combustion 

 of one pound of candles. By this supposition 16 lbs. of pow- 

 der in the expenditure of a mine, will represent the effect of 

 one pound of tallow in combustion." 



Respecting the effect of the animal heat of the miners evolved 

 during respiration in contributing to raise the temperature 

 of the mines. Dr. Forbes observes, after some introductory 

 remarks, " It is probable that the whole of the expired air is 

 not raised to the temperature of the body ; it is also certain 

 that the mean temperature of air in mines is considerably above 

 the mean of the climate : making allowances, then, tor both 

 these circumstances, it will perhaps not be far from the truth 

 to suppose that the air respired by our miners receives an aug- 

 mentation of only 'oO°. From these data we shall obtain the 

 following results : the respiration of a single miner in 2't hours 

 will raise the temperature of 19,980 cubic feet of air 1°; 9990 

 cubic feet, 2°; G660 cubic feet, 3°; 4995 cubic feet, 4°; and 

 so on. Applied to the elevation of the temperature of watei", 

 the results will be in the same time — 48 gallons, raised 1°; 



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