14S OL'scnaiio/ii on tFie Change of 



to the coal, are found lumps of a bright yellow loam, ex- 

 tremely light, and so saturated with petroleum, that they 

 burn like sealing-wax, emitting a very agreeable and aro- 

 matic scent*." 



This substance I also observed when I visited the Bovey 

 coal-pits in 1794 and 179fi- At that time, however, it was 

 scarce, and I could only procure one small specimen, which 

 is now in the British Museum ; but from a cursory exa- 

 mination of it, I was convinced that it was a peculiar bitu- 

 minous substance, and not loam impregnated with petro- 

 leum, as Dr. Milles had supposed. I could not then con- 

 veniently make a regular analysis of it, and therefore con- 

 tented myself with briefly describing it in a note annexed 

 to my paper on bituminous substances f. 



Lately, however, my friend John Sheldon, esq. of Exe- 

 ter, F.R. S., obligino'ly sent me several pieces of it, toge- 

 ther with specimens of the different kinds of Bovey coal 

 xwhich have been mentioned ; and thus I was enabled fully 

 to ascertain its real nature and properties. 



Description of the Bitumen from Bovey. 



It accompanies the Bovey coal in the manner already de- 

 scribed, and is found in masses of a moderate size. 



The colour is pale brownish ochraceous yellow. 



The fracture is imperfectly conchoidal. 



It appears earthv externallvj but when broken exhibits 

 a slight degree of vitreous lustre. 



l"he fraiiments are irregularly angular, and completely 

 opaque at the edges. 



Jt is extremely brittle. 



It does not apparentlv become softened when held for 

 some time in the hand, but emits a faint resinous odour. 



The i-pccific gravity at temperature C5° of Fahrenheit i^ 

 1-135. 



Some specimens have dark spots, slightly approaching iti 

 colour atid lustre to asplialtum ; and small portions of the 

 Bovey coal are commonly interspersed in the larger masses 

 of this bitumen. 



When placed on a heated iron, it imiiicdiafelv melts, 

 smokes much, burns with a bright flame, and vields a very 

 fragrant odoui, like some of the sweet-scented resins, but 

 which at last becomes slightly tainted with th.at of as- 

 phalt um. 



• Philosophifnl Transnctions, vol. li. p. 536. 



f TransiKfe'ilb cf lUt Liiincan Sccitty, vol. iv. p. 139. 



The 



