Observations on bituminous substances, with a description of the varieties of the elastic bitumen ... Read in the Linnaean Soc / by Charles Hatchett.

  • Hatchett, Charles, 1765?-1847.
Date:
[1798]
Catalogue details

Licence: Public Domain Mark

Credit: Observations on bituminous substances, with a description of the varieties of the elastic bitumen ... Read in the Linnaean Soc / by Charles Hatchett. Source: Wellcome Collection.

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    JET. Jet is a fubflance well known to be of a full black, fometimes however inclining to brown. It is confiderably harder and lefs brittle than afphaltum. It breaks with a conchoidai fraCture, and the internal luftre is glafly. It has no odour except when heated* and it then refembles afphaltum. It melts in a ftrong heat, and* when burned, leaves an earthy refiduum. Wallerius confidered jet as afphaltum which had become indu¬ rated by time, and Mr. Fourcroy is of the fame opinion*. Others again have arranged it with the varieties of coal j*. I am inclined however to believe, that it is neither afphaltum nor coal, but an intermediate fubflance which may be regarded as the fifft gradation from the fimple bitumens into thofe which are compound. The matter of afphaltum undoubtedly enters into it in a large pro* portion, and has confequently ftamped feveral of its characters Upon it; but the increafe of carbon, and of the extraneous or earthy matter which is intimately mixed or rather combined with it, has had fo much influence, that the characters of coal are alfo in fome meafure apparent, and are rendered the more ftriking by the fimilarity of certain local circumftances Which attend thefe two fubflances. The characters of coal are however by no means fully eftablifhed in jet, but from this we pafs imme¬ diately to another, in which thefe characters cannot be queftioned* This is the fubflance called CANNEL COAL, which is of a full black, of a fmooth, folid, even texture ; it breaks in any direction, and the tranlverfe fraCture is conchoidai. It * Elemens d'HiJl. Nat. et de Chititie, tom. iii- p. 456. \ Widenmatin s Handbuch der Mineraiogie, p; 62£ ■ ' ' burns