Mr. Harcuery’s.Obfervations on Bituminous Subftances 15% 
ort ij : - B, No. 6. t oils 
Elaftic bitumen, the whole mafs of which refembles fine cork.— 
The fpecific Bal is 0,9748. 
B, No. 7. 
Bi he fame, but friable, and apparently ait by decompofition 
into an ochraceous coloured powder. 
. : 
THE varieties of the firft {pecies of the elaftic bitumen, or that 
which is like the cahout-chou, evidently appear to be formed from 
a maptha or petroleum, which, like that which produces the other 
Simple bituminous fubftances formerly mentioned, is fufceptible of 
"various degrees of infpiffation. 
All the varieties of the firft fpecies, from. No. 1, to No.. 15, may 
be regarded as thus formed, for in thefe we can trace all the modi- 
fications comprehended between petroleum and afphaltum; with 
this difference, that the intermediate modifications of this {pecies 
have the remarkable property of elafticity, which is the moft com- 
plete in the variety which apenbies the middle place between pe- 
troleum and afphaltum, |. 
The fecond fpecies B, or that shiek Seierablee cork, appears fo 
different from that marked A, that it is not at firft eafy to conceive 
how they are connected, or at leaft the difficulty muft appear great 
to thofe who have only feen {pecimens of cach fpecies complete in 
their refpective characters. But, from an attentive examination of 
many {pecimens, and particularly of thofe which I have defcribed, 
{am convinced that the varieties of the fpecies B. are only modi- 
fications of the fpecies A, produced probably by long maceration 
in the water of the rivulet in which this fpecies is found, to the 
effects of which hwe'aiay}) with fome appearance of reafon, add the 
tie viciffitudes 
