152 Mr, Hatchett'j Obfervatlom on Mum'tnoia Subjhr.ces. 



viciffitudes of the feafons, of air, and of the weather in general, 

 as. well as thole of reiterated moid are and diynefs occafioned by 

 the rife and fall of the water of the rivulet j and what feems to 

 corrohorate this opinion is, that the fubftance, like cork, iricrufts 

 the fpecies A, and appears to be only a change which has pene- 

 trated deeper into the fubflance of it in proportion to the duration 

 of the caufes which I have mentioned, fc that at length the origi- 

 nal fubftance no longer remains in its primitive ftate. I do not 

 believe, however, that this change arifes from any alteration in the 

 conftituent principles, but merely from a partial and minute dis- 

 union or difintegration of the particles of the original fubflance, as 

 both fpecies melt into one which is perfectly fimilar. I muft alfo 

 add, that the fpecies A burns eafily, and with rapidity; but the 

 fpecies B burns with fome difficulty, and crackles as if it had im- 

 bibed a quantity of water. 



I have remarked, when the different varieties of the elaftic bitu- 

 men were melted, that they completely loft the elaflic property, and 

 a quantity of air or gas appeared to be difengaged, particularly from 

 the fpecies B. I alfo obferved, that the fubftances which remained 

 after this operation, correfponded, in refpeft to confidence, with thofe 

 which had been employed, as the following Table will fhew : 



A, No. 7 and 8. ... produced a thick liquid petroleum, not appa- 



rently different from that which is commonly 

 known. 



A, No. 9 produced a thicker petroleum, approaching; to 



mineral tar. 

 A, No. 11 and 12. produced mineral tar. 



B ' N r °* 6 produced the fame, approaching to mineral pitch. 



A ' Na l 3 produced mineral pitch. 



A, No. E 4 and 15. did not foffcr any change, but remained as at 



tirft, with all the charades of afphaltum. 



5 From 



