ae hire HETT’s Odfervations on Bituminous Subfances, «4s 
§.5- 
LITTLE need be faid concerning thofe mixtures of bitumen 
with metals or their oxides which are fometimes called the bitumi- 
mous ores of mercury, copper and iron, for they fhould rather be 
arranged with the adulterated or impure bitumens. Few of them 
contain 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 Carniola, 
compofed of mercury mixed with bituminous matter, a quintal 
of which, according to Mr. de Born, affords from fifteen to twenty 
pounds of mercury *, 
§ 6. 
FROM the preceding obfervations it will appear, that although I 
have firft mentioned naptha in order that I might be better un- 
derftood in refpeét to the degree of conneétion prevailing between 
the bituminous fubftances, yet, to have followed them from. their 
origin and the period of their formation, I thould rather have begun 
with thofe fubftances which moft clearly point out how much 
the vegetable kingdom has contributed to the produétion of them, 
with the probable occafional concurrence of animal fubftances. 
That the latter have contributed in fome meafure to the forming 
ef bitumen, we can only infer from the veftiges and exuvie of 
animals, which fo commonly nse bituminous fubftances ; ; 
papiertorf. durch den moor oder fumpftorf in den pechtorf, und. von aiefem in dic 
braun fchiefer und pechkohle.— WVidenmann, p. 630. 
® Catalogue dela CollePion des Foffiles de Me de Raab, tom, ii. p, 204, 348, & 400. 
iy o1, IV. U but 
