147 



but sometimes the same piece is less elastic in one part than an- 

 other. On burning it, the smell is rather pleasant. 



The varieties of this fossil, described by Mr. Mawes, are 1. 

 Elastic bitumen, of a reddish brown colour, containing nodules of 

 indurated shining black bitumen, resembling jet. 2. A piece in a 

 marine shell, in lime-stone. 3 Dull, red and transparent, in cry- 

 stallized rluor. 4. Composed of filaments, like soft cauk, and of a 

 singular acid taste. 5. Indurated amorphous masses and globules 

 of a shining black, like jet ; sometimes liver-coloured ; electric, 

 when rubbed. 6. With asphaltum, and containing lead ore; and 

 the same in long filaments, almost as fine as wire. 



A considerable spring of petroleum exists at Colebrook Dale. 

 Tins spring was discovered at about thirty yards in depth, whilst 

 digging to form an archway to convey the coals from a very deep 

 pit. It was at first found to ooze from between the crannies of the 

 rock, but soon began to pour out in a considerable stream, run- 

 ning even into the Severn. Large iron pipes are employed for the 

 conveyance of the fluid into proportionably sized pits, which have 

 been sunk for its reception. Hence it is conveyed into immense 

 caldrons, in which it is inspissated, by boiling, to the consistence of 

 pitch. Whilst fluid, the tar, which appears to be remarkably free 

 from impurity, has rather an agreeable odour; and when inspissated, 

 it exactly resembles the asphaltum of the Dead Sea. Since its first 

 discovery, three different springs of it have broken out, one of 

 which pours out a considerable quantity. Near to the celebrated 

 iron bridge, this bituminous fluid is emitted pretty copiously, being 

 almost pellucid, but thicker than treacle. A similar rock with that 

 from which the petroleum flows may be traced upwards of seven 

 miles ; the coals, which are found at some depth beneath, the petro- 

 leum, are of an exceeding good quality. 



From the experiments of Mons. Boulduc*, made on naphtha, 



* Histoire FAcadem. Royale des Sciences, 1115, p. 15. 



