Mr. HatchettV Obfervatiom on Bituminous Subflances. 15- 



From what I have related, I fufpe& that the elaftic property 

 is occafioned by the interpofition of veiy 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 elaftic 

 fluid is liberated, and the mafs lofes that fine fpongy texture which 

 I fufpec~t to have been the caufe of the elaftic property* 



Derby (hire 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 foflils, fuch 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 Derbyftiire. 



Whoever has examined the limeftone rocks about Matlock, and 

 moft other places in this county, muft be convinced of the truth of 

 this aflertion. 



The limeftone and calcareous fpars alfo, where the elaftic bitu- 

 men is found, are, for the greater part, in the lame ftate ; fo that no 

 doubt can be entertained but that this bitumen has had the fame 

 origin as thofe which are more generally known ; and it would 



* The elaftic bitumen, A, No. 9. when digefted in fulphuric ether in a temperature of 

 about 55 , is partly diflblved. The folution is yellowifh brown when oppofed to the light ; 

 but when otherwife viewed, is like the bitumen, that is, of a brownifti olive colour. By 

 fpontaneous evaporation, the etheric folution leaves a yellowifh brown bitumen, which 

 is totally devoid of elaflicity. The undifTolved 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 refpecte it is but little affected. 



Vol. IV. X undoubtedly 



