THE EARTH. 61 



Thus, the vapours found beneath the surface of the earth are 

 very various in their effects upon the constitution : and thoy are 

 not less in their appearances. There are many kinds that seem- 

 ingly are no way prejudicial to health, but in which the workmen 



est flame of coals ; sometimes the upper part of the mine next tlie roof lias 

 the air perfectly good, while the pavement has a stratum of carbonic acid, of 

 a foot or two in thickness, resting upon it. 



As the flame of a candle is a correct index of the presence of this air, the 

 miners have instant warning, and stop their advancing any farther, till means 

 are used to drive it away. Comparatively few lives have been lost by this 

 gas. Those who have perished from its effects, had generally gone amongst 

 it without a candle, and of course were insensible of its presence, till they 

 dropped down from its deleterious efifects on the constitution. When men 

 are rendered senseless by inhaling this air, they can be recovered if brought 

 quickly into good air, but if they remain any time in it, all attempts to re- 

 cover them are incflfectual. It must be remarked, however, that as the air 

 of tl-3se coal mines which abound with carbonic acid, has always a very con- 

 siderable mixture of it through the whole of the works, the air in this state 

 is reckoned very salubrious, though mixed with a great proportion of mois- 

 ture. The workmen who breathe it every day are generally healthy, and it 

 is reckoned a specific in some complaints, it being a common practice to send 

 down children aflfected with the hooping cotigh to breathe in it 



The carburetted hydrogen is not found in all coal mines, and is seldom seen 

 where the carbonic acid abounds. In Scotland there are extensive districts 

 where the inflammable air was never seen, and others xvhere it is very abun. 

 dant In the numerous collieries situated upon the north banks of the river 

 Forth, it is only found in one very limited district, and in only two districts 

 upon the south banks of the Forth. In the very extensive coal-fields in the Lo- 

 thians, south from the city of Edinburgh, it is unknown : whereas in the coal, 

 fields around the city of Glasgow, and along the coast of Ayr, it is found very 

 abundant ; at the same time there are coal-fields in that very extensive range, 

 where it never was seen ; but where it is not seen, the carbonic acid abounds. 



The production of these gases, renders the system of the ventilation of coal 

 mines a chief point in the system of mining, particularly where the iuflajnraa. 

 ble air abounds, by wliich the lives of the workmen and the prosperity of the 

 mining concern may be instantly destroyed. It would require a long disser. 

 tation, and the mosc minute detail, to give a clear view of the almost infinite 

 variety of cases connected with the accumulation of inflammable air in the 

 mines of a colliery, and of the plans and methods which have to be employed 

 and varied for the ventilation, corresponding to each pai'ticular situation of 

 the mines. 



With daily misfortunes of a lesser or greater degree were the collieries of 

 Great Britain carried on from year to year, every one struggling against the 

 direful ravages of the inflammable air : but it baflled the skill of the most ex- 

 perienced engineers, and all the precautions of their most unwearied diligence 

 and anxious attention. The general question and anxious inquiries were. Can 

 no remedy be devised to avert these awful calamities, to deliver an indus- 

 trious class of society from such desolating catastrophes ? Many plans were 

 proposed, but they were altogether inapplicable. , 



