MINE. 



561 



tion. 



Every bed of coal abounds less or more with delete- 

 *' * 1 ' rious air, which is of two kinds ; the one is specifically 

 ^' nfav ' er < ^ otner lighter than common air; the natu- 

 ra ' coi**<] uence f which is, that the one rests in the 

 deepest or lowest places, the other, from its levity, 

 ascends to the highest places of the min .. The first 

 is known by the common provincial names of choak 

 damp, black dump, styth, or bad air ; the other is 

 known by t.ie name of foul air, fire-damp, or inflam- 

 mable air. The one is the carbonic acid, the other 

 the carburetted hydrogen gas of the chemi-t. 



The precise qualities of the carbonic acid of coal 

 mines, have been comparatively little attended to, as 

 its destroying powers have not operated extensive- 



ly 



The nature and composition of the carburetted hy- 

 drogen have closely engaged the attention of philoso- 

 phers tor the last ten years. 



According to the best authorities these gate* are of 

 the following specific gravity and weight. 



Mines of 

 Coal. 



Carbonic acid 

 Carburetted hydrogen 

 Hydrogtn 



Spec. Gnv. 

 1 518 

 0.535 

 0.074 



Wsijbt aflOO 

 Cubic India. 

 4&SIS 

 16.99 

 2.SSO 



The common air being reckoned unity, the tempera- 

 ture at 60, and barometer at 30 inches. 



According to Dr Thomson, the component parts of 

 carburetted hydrogen are. 



Carbon 7* 



28 



100 



Exploding In which there is always a mixture of carbonic add. 

 P *" 1 of It has been found that this gas has its greatest ex- 



'"" plosive power when it is mixed in the propoition of one 



part of gas to eight parts atmospheric air ; and when 

 it M in the proportion of one part to fifteen of atmo- 

 pheric air, a candle burns in it without explosion, luit 

 trie flame is greatly elongated ; it therefore ought 

 to be diluted with common air considerably beyond 

 that proportion, to insure the tafety of the work- 

 men. 



Various theories have been brought forward regard- 

 ing the formation of these gases, but more particularly 

 of the carlxtreted hydrogen : both of them flow or ex- 

 ude from the cutters, fissures, and minute pores of the 

 coal; and when in small quantity in the forehead of a 

 mine in solid coal, they make a hissing noise. 

 Catbeoic The carbonic acid seldom comes olf very suddenly 



inc. 1 . i n Urge quantities. From its weight it it not liable to 



sudden change of pi ice, and though it is invisible, 

 its line of division from the common atmospheric air 

 is most distinctly found by approaching it with a light- 

 ad candle or lamp ; for though the candle burns with 

 its ordinary brightness at the distance of t'mc inches 

 from the carbonic acid, the instant it is placed within 

 this air, it is suddenly extinguished ; it produces the 

 same instant effect upon the strongest flame of coals ; 

 sometimes the upper part of the mine next the roof 

 baa the air perfec.ly good, while the pavement has a 

 stratum of carbonic acid, of a foot or two in thickness, 

 i If a coal hii a considerable dip and 

 rUe, this gas will be found occupying the lower parts 

 PLATE of ill t a wedge form, as represented Fig. 5 



eeiriii. Platt (. v. ( \( III. where a is the carbonic acid ai.d 6 

 * * the cumn.uii air. When this gas is agitated by cur. 

 VOL. nr. FART u. 



rent of common air, or by falls from the roof, it 

 mixes with the mass of common air, and affecU the 

 candle by gradually diminishing the flame ; and when VentilaT" 

 a stronger portion of the mixture is entered into, the tiun. 

 candle is extinguished, but not in the very sudden 

 manner as before mentioned. 



When a mine or forehead is driving in advance of 

 the other workings, and a discharge of this air takes 

 place, it very soon fills the whole mine, if the direc- 

 tion of the mine is in the line of level, and the mine is 

 rendered unworkable until a supply of fresh air is 

 brought to displace 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 hav 

 been lost by this gag. 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 effects 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 recover them are ineffectual. It 

 must be remarked, however, that as the air of these 

 coal mines which abound with carbonic acid, has al- 

 ways a very considerable mixture of it through the 

 whole of the work, the air in this state is reckon- 

 ed very salubrious, though mixed with a great propor- 

 tion of moisture. 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 affected with the hooping cough to 

 breathe in it. 



The carburetted hydrogen is not found in all coal Ourburet- 

 mines. and is seldom seen where the carbonic acid "<' hjdro- 

 abounds. It has hitherto lieen found in the greatest K en - 

 quantity in the coal-mines situated in the counties of 

 Northumberland, Uurliam, Cumlierland, Staffordshire, 

 anil Shropshire. And from invr-ti^ation we tind, that 

 it ia generally much more abundant in cauls which are 

 of a fine caking quality, and which have a bright 

 steel grained fracture, than in cubic coal* of an open 

 burning kind, and the cubic open burning coals 

 yield spontaneously in general more of this gas than 

 the splint coals. To these general cases there are, 

 hot-ever, exceptions, come ol them very remarkable; 

 few of which we shall now nc.ti c. 



In the coal-fields of England and Wales, there are England 

 district* where this gas abounds, and other districts and Wain, 

 where it i never seen ; not only so, but in some ex- 

 tended coal-fields it will be found very abundant upon 

 one range of the line of bearing, whereas upon the 

 other range none of it is to be seen, but abundance of 

 carbonic acid. 



In Scotland the same general remarks are applies- Scotland. 

 We, there being extensive districts where the inflam- 

 mable air was never seen, and others where it is very 

 abundant. In the numerous collieries situated upon 

 th< north banks of the river Forth, it is only found in 

 one very limited district, and in only two districts 

 upon the south Kink- of the Forth. In the very ux- 

 cn.-il-fields in the I-othians, south from the city 

 ni I .ilinburgh, it is unkn >wn : whereas in the coal- 

 fields around the city ,,t (ilasgow, and along the coast 

 of Ayr, it is found very abundant ; at the same time 

 there are coal fit-Ills in that very extensive range, . 

 where it never was seen ; but where it is not seen, the 

 carbonic acid abounds as before mentioned. 



22 



