X%z Mr. Hat chett'j Obfervalions on Bituminous Sub/lancet 



MOUNTAIN or MINERAL PITCH— Bitumen Maltha. 



The mineral pitch much refembles common pitch, and, when 

 heated, emits a ftrong unpleafant odour, like the former fubftance. 

 When the weather is cold, it may be broken, and then exhibits, 

 internally, a glaffy luftre ; but when warm, it is foftened, and pafV 

 feifes fomc tenacity. It is however fufceptible of a fuperior degree 

 of induration, and then becomes 



ASPHALTUM — Bitumen Asphaltum — Petroleum 



INIMJRATUM. 



Tms is a light, brittle fubftance, of atrownifh black, or black. 

 When broken, it fhews a conchoidal fracture with a glaffy luftre, 

 It has little of the bituminous odour, unlefs it is rubbed or heated. 

 It eafily melts, is very inflammable, and, when pure, burns without 

 leaving any allies.. 



In this manner, naptha v byinfpiifation,.pafles fuccefnVely through 

 different ftates until it becomes afphaltum, which appears to be the 

 ultimate degree of induration which the pure bitumens derived 

 from naptha can receive; 



1 have at this time fpecimens before me which prove theffe 

 gradations; and I have feen a remarkable inftance in a bitumen 

 brought from the Ifland of Trinidad, which exhibits mineral tar 

 pafling into mineral pitch, and laftly into afphaltum*.. 



§ i; 



* The progreffive changes ©f naptha into petroleum, mineral tar* mineral pitch, and 



afphaltum, appears to be caufed by the gradual diffipation of part cf the hydrogen of 



the bitumen, and the confequent development or difengagement of carbon. Hence, I 



am inclined to believe, arife the changes of colour, the degrees of infpiflation, and 



'the increafed proportion of carbon found in thofe fubfhnces by chemical analyfis. 



I would; 



