respecting the Temperature of Mines. 105 



will of course be in proportion to the depth of the mine. The 

 air thus heated traverses the works, and imparts its heat to 

 the strata ; it then ascends, and is succeeded by a fresh portion 

 of air fi-om the surface, which in the same way becomes heated, 

 and imparts its heat to the strata, and they, in turn, commu- 

 nicate it all around. Tlius in a long course of working in a 

 deep mine, the air at the bottom is heated, and also the rocks 

 to a considerable depth ; and when the woi'king ceases, the mine 

 takes a long time to lose its temperature ; and this is found to 

 be the case particularly when the mine becomes full of water, 

 the water being found at first of a high temperature, and gra- 

 dually to lose its heat, which is in consequence of the strata 

 imparting theirs to the water ; and as soon as they have given 

 out all their heat, the water indicates the mean temperature 

 nearly of the place. 



" The reverse takes place in an old mine when reworked ; 

 in that case, the temperature rises gradually as the working 

 continues : and in those mines which are not worked, but in 

 which the ventilation still goes on, I believe it will be found 

 that they do not lose more of their temperature than can be 

 placed to the abstraction of the other causes of heat in working 

 mines, such as that produced by the men and the lights. 



" The exact quantity of heat given out by air in proportion 

 to its condensation, it is difficult to ascertain ; but every day's 

 experience proves it to be very considerable ; and, I believe, 

 this, added to the other obvious soiurces of heat in mmes in a 

 state of workinjr, will be found sufficient to account for their 



high temperature." 



We will now close this article, for the extent of which the 

 great importance of the subject must be our apology, with a 

 brief abstract of a paper " On the Temperature of Air and of 

 Water in the Coal Mines of Great Britain " by Mr. Robert 

 Bald, F.R.S. E. &c. (Read before the Royal Society of Edin- 

 burgh in 1819) as given in the Edinbm-gh Philosophical Jour- 

 nal, vol. i. p. 134. 



" The increase of temperature in coal mines, is a fact fami- 

 liar to every person who has had occasion to frequent them- 

 The instant a dijvpit is connected with a rise-pit by a mine, a 

 strong circulation of air like wind commences. If the air at 

 the surface is at the freezing point, it descends the dip or 

 deepest pit, freezes all the water upon the sides of the pit, and 

 even forms icicles upon the roof of the coal within the mine ; 

 but the same air, in its passage through the mines to the rise- 

 pit, which is generally of less depth, has its temperature greatly 

 increased, and issues from the pit-mouth in the form of a dense 

 misty cloud, formed by the condensation of the natural vapour 

 of the mine in the freezing atmospkere." 



Vol. G2. No. 301. Aug. 1823. O " The 



