Proportions of Carbon in Mineral Com/. a a ? 



to its decompofition, but were taken up by the air it fpontaneoufly emitted, and partly by the 

 ambient atmofpheric air, 



jijphalt. 



ITS colour is greylfh black. Luftre 2.3. greafy. Tranfparency o. 



Frafture perfedVly conchoidal. Hardnefs from 7 to 8, very brittle. Specific gravity from 

 1,07 to 1,165 by^y trials. It feels fmooth, but not greafy; has no fmell, except while 

 pounding ; does not (lain the fingers ; when heated it melts, fwells, and at laft inflames \ 

 but it requires, for inflammation, a higher heat than maltha does, and leaves no coal, and 

 fcarce any afhes. 



Of this bitumen I found i6r grains requifite to alkalize the ftandard quantity of nitre : 

 it vifiblyeduced air from the nitre ; for there were eruptions from time to time. 1 fuppofe 

 when the more oily part was confumed, and the carbonaceous laid bare, much of the flame 

 was alfo yellowifli. Hence 161 grains of afphah contain only 50 of mere carbon, that is, 

 nearly 3 1 per cent. 



Mr. Thory, burning it in a low heat, found It to leave about of its weight of coal 

 after melting, fwelling and inflaming as ufual *: however, his afphalt was not perfedlly pure, 

 as he obtained fulphur from it. 



Cannel Coal. 



ITS colour Is black. Luftre 2. Gommon when frefh broken, often barely I. Tranfpa- 

 rency o. ■ '• ■ •'■ ■■'■'■• ; ■ 



Crofs frafture conchoidal. Fragments rather fharp. Hardnefs from 7 to 8. Specific 

 gravity by my trials 1,232, by Dr. Watfon's 1,273 ; does not ftain the fingers, eafily 

 kindles without melting, and burns with a large bright flame, but of fliort duration, leav- 

 ing a large coaly reCduum ; does not cake. 240 grains of it, heated until all the coaly part 

 was confumed, left 7,5 grains of reddifli brown afties, moftly argillaceous, that is, 3,1?. 

 per cent. 



66,5 grains of it were fuflicient to alkalize the ftandard quantity of nitre. It burned with 

 a large bright flame, except the laft portion, which was yellowiflj, the pure air of the nitre 

 being then exhaufted. Hence 66,5 grains contained 50 of pure carbon, and 2,08 of afhes ; 

 then deducing 52,08 from 66,j, we find the quantity of bitumen equal J4,42. Then 

 100 parts of it contain 75,2 of carbon, 21,68 bitumen of the fort called maltha, and 3,1 of 

 afhes. 



I take this bitumen to be maltha, from Its quick Inflammability, and the fhort duration 

 and brightnefs of Its flame, both which properties indicate the moft inflammable of the 

 bitumens, and whofe flame is leaft durable from its refufal to cake (caking being a pro- 

 perty arlfing from the fufion of afphalt), and the difficult combufllbillty of the carbonaceous 

 fubflance that remains after the ceffatlon of its flame — qualities that counter-indicate afphalt. 



Stoty Cannel Coal. 

 THAT which I employed was from Ayrfliire ia ^9fty4t{i<l>< 'he onjy. ,<)fl<j ,of thi« /prt. .im- 

 ported to Dublin. ; , :][>, nl ^i\ .! j',.i! )■) 11 r.lfi -ii-i' .; 

 Its colour is black. .... .1,' .."'.• ' :,,r\ ■ .. v, , . 



• 6 Crtll's Chjm. Jour, ii. 



Its 



