948 Obfervatmi on Bitumens, 



bonic ac'd, This produ£tl0n of carbonic acid, therefore, adds to the dilatation occafioncd 

 by the evolution of hydrogenous gas. 



6. There is not, by the adtion of the cledric matter on carbonated hydrogenous gas, any 

 generation of azotic gas. 



7, Carbon, it appears, therefore, from the united evidence of thefe faifls, is ftill to be con- 

 fjdered as an elementary body s that is, as a body with the compoGtion of which wc are unac- 

 quainted, but which may neverthelefs yield to the labours of fome future and more fuccefsful 

 analyft. 



II. 



OlfervaUot7s on Bituminous SubJIances, with a Defcr'tplion of the Farteties of the Ehjlic 

 Bitumen. By CHARLES Hatchett, Efq. F.R.S. Lond. and Edin. F.L.S. U'c 



£ConcIiided from Page 209, Vol.II.] 



X H E chara£ters of bitumen are much more apparent in turf and peat, than in the 

 greater part of the foflil woods. Turf is well known to be compofed of the parts of vegetables, 

 fuch as fmall roots, twigs, &c. mixed with a portion of petroleum ; and peat is the fame, 

 excepting that it generally contains more of earthy matter, or that the vegetables have 

 undergone a more complete decompofition. 



The boggy nature of the places in which they are found, proves that a certain degree of 

 maceration is neceflary to form the bituminous matter which they contain ; and I have 

 already noticed, that every fadi appears to demonftrate, that the bitumen is a produ6l of 

 thofe vegetables, the remains of which conftitute the other ingredient of turf and peat. 



The different proportion of vegetable matter, of bitumen, and of earth, together with the 

 different ftate of the bitumen, as well as the degree of perfeiStion refpefting the formation of 

 it from tlie vegetable principles, contribute to alter the properties and charadlers of the 

 compound, and thus produce varieties. It is believed that thefe fubftances have been 

 materially concerned in the formation of pit-coal, and fome eminent mineralogifts maintain 

 that there is an uninterrupted feries which conne6ls the varieties of turf and peat with thofe 

 of coal *. 



SECT. V. 



LITTLE need be faid concerning thofe mixtures of bitumen with meta'i or their oxides 

 which are fomctimes called the bituminous ores of mercury, copper and iron, for they 

 fhould rather be arranged with the adulterated or impure bitumens. Few of them contaia 

 the metallic ingredient in a proportion fufficient to caufe the compound to be worked as an 

 ore ; and the only exception with which I am acquainted, is the fubftance found at Idria, in 

 Carniolia, compofed of mercury mixed with bituminous matter, a quintal of which, accord- 

 ing to Mn de Born, affords from fifteen to twenty pounds of mercury f . 



• Man findet in der natur einen vinunterbrochenen ijbergang von dem rafen und papiertorf durch den moor 

 ■•der fumpftorf in den pcchtorf, und von diefem in die braun fchiefer und pechkohle. — Widenmann, p. 630, 

 t Catalogue dela Colkftion des Foffiles de Mite, de Raab, torn. ii.p. i94, 348, and 400. 



SECT. VI. 



