Ag^ Proportions of Carbon m M'trui-al Coat. 



Its luftre I. Common. Tranfparcncy o. ■ 



Its fracture partly flaty, partly imperfectly conchoidal-, fragments ■ iftianw ; . 



Its hardnefs from 5 to 8. Specific gravity 1,426 by my trials. 



It burns like the coropaiSt canucl, but ccafcs fooncr to flame ; does not cal^e— leave* a 

 Aony refiduum. 340 grains of it, treated as before mentioned^ leave 50 of leddifli grey 

 aflies, equal 20,83 per cent. From the fmeJi, tl^at iifues frara it during igpition, I am led to 

 think it contains fome portion of fulpbur- •••,■,., 



To alkalize 480 grains of nitre, icj gpii^s of this coal were employed. It burned like 

 the former with a large white continued llame, except the laft portions. Hence this quan- 

 tity contained 50 grains of mere carbon ; and Gnce it alfo eontaiued 20,83 °^ afhes, the 

 remainder, namely 34,15, muft have been bitumen. Then 100 parts of it contain 47,62 of 

 carbon, 32,52 of bitumen, and about 20 of aflics. Some dedudion however from thcfc 

 quantities of carbon and bitumen may be made by reafon of the fmall proportion of fulphur 

 contained in it. This bitumen I take to be maltha, and not afphalt, for the reafons I men- 

 tioned in treating of compact cannel. • . 



it is from a coal of this fort tliat Lord Dundonald extrafts his tar, as maltha eafily diftiU •, 

 but it is probably of a better kind, as this flony kind exifts moftly in Ayrihire. 



By his Lordfliip's mode of diftiUation, however, much feems to be loft during tlie internal 

 combuftion. I {hould think the Prince of Naflau Saarbruck'j metliod in this refpe£t more 

 advantageous. Mr. Sage tells us, tliat, by diftillation, he obtained from cannel coal ^ of its 

 weight of tar* ; but Mr. Faujas, who ufes Lord Dundonald's method, obtains from the 

 coal of Decire, which feems to be of this kind, only 4 per cent, of tar f. Faujas alfo ob- 

 fen-ed, that this tar is gradually converted into afphalt by long expofure to the air, wliicl^ 

 confirms tlie difference I have eftabliflied between the two bitumens, 



Wnirtehav'en "Coal'. 



■ •■•■,' ' ■ " 

 ITS colour is black. 



Its luftre 3. Greafy. Tranfparency o. 



Its fracture plane foliated. Its fragments 2, often difcovering quadrangular or cubie 

 diftinct concretions, fometimes interfected with brownifli red flakes. 



Its hardnefs 6, very brittle. Specific gravity 1,257 by my trials. Stains the finger*, 

 particularly when moift. 



It burns at firft with a clear flame, and for a long time ; but at laft cakes. 240 grains of 

 it, after five hours ftrong heat, left only 4 grains of reddifti alhes, or about 1,7 per cent.' 



The ftandard quantity of nitre was alkalized by 88 grains of this coal. Hence 100 graint 

 of it contained nearly 57 of mere carbon, 41,3 of a mixture of maltha and afphalt, and 1,7 of 

 a(hes. That it contains both maltha and afphalt is evident from its flame and caking. The 

 proportion I. cannot exaftly afcertain, but moft probably the afphalt predominates. 



Wigan CoaL 

 ITS colour is black. 

 Its luftre 3. Greafy. Tranfparency ». 



Its fradlure plane foliated. The lameilx, fomc uniformly, fome promifcuoufly directed. 

 In the grofs often flaty ; forms fcparate concretions, often with bright yellowilh illinitions. 

 * Roi. Journ. p. 387. + R02. Joum. p, 18S. 



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