Mr. Hatcuett’s Objervations on Bituminous Subpances. 153 
From what I have related, I fufpeét that the elaftic property 
is occafioned by the interpofition of very minute portions of air 
or fome other elaftic fluid between the parts of the bitumen, and 
that this takes place by reafon of fome unknown caufe at the time 
- of formation; but when thefe bitumens are melted, the elattic 
fluid is liberated, and the mafs lofes that fine fpongy texture which 
I fufpeé to have been the caufe of the elaftic property *. 
Derbyfhire is well known as a country which exhibits, in the 
moft ftriking manner, the remarkable changes which our globe has 
fuffered. In every part of it, the moft indifputable evidences ap- 
-pear of fome great and extraordinary revolution; and there is not 
any place where extraneous foffils, {uch as the remains and impref- 
fions of vegetables and animals, are more abundant. 
Bitumen, in other countries, is moft commonly found where 
thefe prefent themfelves; and, in like manner, there are few coun- 
tries which abound fo much with bitumen as Derbythire. 
Whoever has examined the limeftone rocks about Matlock, and 
moft other places in this county, muft be convinced of the truth of 
- this affertion. : 
The limeftone and calcareous fpars alfo, where the elaftic bitu- 
men is found, are, for the greater part, in the fame ftate ; fo that no 
doubt can be entertained but that this bitumen has had the fame 
origin as thofe which are more gencrally known; and it would 
* The elaftic bitumen, A, No. 9. when digefted in fulphuric ether in a temperature of 
about 55°, is partly diflolved. The folution is yellowith brown when oppofed to the light ; 
but when otherwife viewed, is like the bitumen, that is, of a brownith olive colour. By 
f{pontaneous evaporation, the etheric folution leaves a yellowifh brown bitumen, which 
is totally devoid of elafticity. The undiflolved portion (like the cahout-chou under fimi- 
lar circumftances) is foftened, and is much increafed in bulk. 
The fpecies B, No. 6. cut into very thin flices, communicates a yellow tinge to 
fulphuric ether; in other refpeds it is but little affected. 
= Vor. IV. . undoubtedly 
