146 Mr. Harcuert’s Obfrvations on Bituminous Subftances. 
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 proceffes at prefent unknown to us: 
That when certain portions of vegetable matter remain undecom- 
pofed, and are mixed with the petroleum thus produced, the varieties 
‘of turf and peat are formed: ; 
That wood in general contributes to the produdtion of bitu- 
men ; but does not feem to retain it, afterthe formation of it, in fo 
confiderable a proportion as the foregoing fubftances : 
That the bituminous matter thus formed, and occafionally fepa- 
rated, is in different ftates according to the degree of infpiffation :» 
And laftly, with various proportions of carbonic and earthy 
matter, it forms jet, coal, and bituminous fchiftus; and with me- 
tallic fubftances it produces thofe compounds called bituminous 
ores. 
§ 7. 
ABOUT the year 1786 a new fpecies of bitumen was difcovered 
near Caftleton, in Derbyfhire, which much refembles, in elafticity. 
and colour, the fubftance known by the name of cahout-chou, or 
Indian rubber. lave 
Mr: 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 fince 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 
% Catalogue dela Collefion de Me. de Raab, tom. ii. p. 77- e 
or 
¢ 
