Kevj Species if Bitunun refanhUng India Ruhher. 249- 



SECT. VI. 

 ■ FROM the preceding obfervatlous it will appear, that although I have firft mentioneu 

 naptha in order that I might be better underftood in refpeft to the degree of connexion 

 prevailing between the bituminous fubftances ; yet, to have follovfed them from thcii*origira 

 and the period of their formation, I fliould rather have begun with thofe fubftances which 

 nioft clearly point out how much the vegetable kingdom has contributed to the produdlion 

 of them, with the probable occafioual concurrence of animal fubftances. 



That the latter have contributed in fomemeafure to the forming of bitumen, we can only 

 infer from the veftiges and exuvire of animals, which fo commonly accompany bituminous 

 fubftances : but no doubt can be entertained in refpe£t to vegetables ; for it appears that 

 bitumen is formed from- them by long maceration, and by other procefles at prefent un- 

 known to us : 



That when certain portions of vegetable matter remain undecompofed, and are mixed 

 with the petroleum thus produced, the varieties of turf and peat are formed: 



That wood in general contributes to the produdlion of bitumen ; but does not fecm to re- 

 tarn it, after the formation of it, in fo confiderable a proportion as the foregoing fub- 

 fl^^ances : 



That the bituminous matter thus formed, and bccafionally feparated, is in different ftates ■ 

 according to the degree of infpiflation : 



And laftly, with various proportions of carbonic and earthy matter, it forms jet, coal, and 

 bituminous fchiftus; and with metallic fubftances it produces thofe compounds called bitu-^ 

 minous ores, 



SECT. VII. 



ABOUT the year 1786 a new fpecies of bitumen was difcovered near Caftleton, ii; 

 Derbyfhire, which much refembles, in elafticity and colour, the fubftance known by the 

 name of cahout-chou, or Indian rubber. 



M. de Born was, I believe, the firft who mentioned it*; but, as he appears to have 

 known only one variety of this fingular fubftance, I am induced to hope that a defcription - 

 of many other varieties, which have fmce been found, will not be unacceptable to this 

 Society. 



The elaftic bitumen, which refembles the cahout-chou, was firft difcovered in the cavities 

 of a vein in the lead-mine called Odin, which is near the bafe of Mamtor, to the north of :' 

 Caftleton. The ore of this mine (which is fuppofed to be one of the moft ancient in Eng- - » 

 land) is galena, accompanied by fluor, calcareous and heavy fpars, quartz, blende, calamine, 

 felenile, afphaltum, and the elaftic bitumen, although the latter is now rarely found f, , 

 Another fpecies of the elaftic bitumen has within about three years been found in a neigh- 

 bouring rivulet ; but I fhall not at prefent notice it, as I intend firft to deferibe the varieties 

 of that which was firft difcovered, and which refembles the cahout-chou.. In order to do • 

 this with mare perfpicuity, 1 fhall ciefcribe the fpecimens.belojiging to my. ColleiStion, ac«'- 

 cording to the mode in which I have arranged them. 



* Catalogue de la Colleftion de Mile, de Raab.tom. ii. p. 77. 



f I am indtljted to the ingenious Mr. White VVatfon, of Bakewell, .for much information. reQ)e&ing the . 

 local ciicumftancts which attend this bilumeiu 



Voi. Ik— Sept. 1798.: Kk SPECIES 



