30 On the Veittilation of Mines. 



iiient ; but one body may give out heat to anotlicr of a lower 

 temperature, and yet be in the act of conducting heat. 



If some imperfect conductor could have been substituted for 

 the neck of metal, a difference in the quantity of heat generated, 

 in a given time, would no doubt have been the consequence ; 

 but, unfortunately, this mode of varying the experiment did not 

 occur to Count Rumford. 



I am, sir, yours, See. 



XI. 071 the Ventilat'iGn of Mines. By James Watt, M.D. of 



Glasgow. 



To Mr. Tilloch. 



Sib, — X iiE late success of science, in obviating the danger 

 from deleterious gases in mines, must be grateful alike to the 

 philosopher and philanthropist, if you judge the following ideas 

 Qondiicive to the completion of a design so important, your in- 

 sertion of them will much oblige the writer. 



The merit of Sir Humphry Davy's lamp seems to justify its 

 hi"h character. Previous to this invention, the existence of the 

 deadly explosive gas was detected in most cases only by the sad 

 experience of its destructive effects ; now, the danger may be 

 feaiely detected and easily avoided. This lamp, however, does 

 not prevent the production of the gas, nor render the workings 

 safe where it gveatlv abounds. Nor docs it prevent the danger of 

 explosion in other cases, as when a lire is used, at the bottom 

 of the upcast pit, to promote the ventilation. Besides, this 

 lamp is not calcujated to clear the mine of the cnrhovic acid gas^ 

 which, though detected with less danger than the other, is also 

 deleterious to the workmen. Indeed, the principal merit of 

 Davy's invention is, that it enables the miner to detect, by his 

 light, the explosive gas, with equal safety and certairity as he 

 formerly discovered the presence of the other. The most pro- 

 per use of the discovery in botii cases will be the same, — to make 

 his escape, with all practicable expedition, till by the aid of 

 ventilation the enemy be dislodged. 



It is evident then, that though a complete method of ventila- 

 tion would supersede the use and necessity of all such contri- 

 vances as Davy's lamp, however ingenious and sublime ; yet no 

 such invention could supersede the necessity of ventilation. To 

 find a ])lan of ventilation, as practicable and as effectual as pos- 

 sible, is therefore an object of high importance. 



In mines which are furnished with several shafts, a degree of 

 ventilation is for the most part insured by tl.c different tempe- 

 ratures of the atmosphere above and in the interior of the mine. 



In 



