Geological Society. 46l 



other substances produced in the distillation of wood ; and 

 on their analogy with the native Bitumens," was read. 



When wood is submitted to destructive distillation, there 

 is obtained, among other products, a black substance re- 

 semblnig common tar. This tar is very inflammable, and 

 so liquid that it may be burnt in a lamp. i:iy washing it 

 with water either hot or cold, or submitting it to the action 

 ol^ hme or of the mild alkalies, a large portion of acetic 

 acid is separated, and the residue becomes pitchy and tena- 

 cious. It is entirely soluble in caustic alkali, in alcohol, 

 in ether, in acetic acid, and in the mineral acids. The fat 

 oils and the recent essential oils dissolve but little of it ; but 

 it the former are made dryins:, and if the latter have become 

 brown by keeping, they then act more readily and copi- 

 ously. Coloured oil of turpentine takes up a considerable 

 quantity, but naphiha only acquires a scarcely sensible 

 brown colour by digestion upon it. When cai-efuliy di- 

 stilled at a gentle heat it is decomposed into an oily mat- 

 ter, at first limpid and afterwards brown, a quantity of 

 acetic acid combined with a little ammonia; and a spongy 

 coal remains in the retort. In this process no inflammable 

 gas is given out; but at a high temperature the oil is more 

 or less decomposed, and an inflammable gas is produced, 

 which, however, does not burn wuh a flanie by any means 

 so bright as the gas i'rom pit-coal. If this destructive di- 

 stillation is not carried very far, the matter in the retort 

 will be found, when cold, to be solid, brilliant, shining, 

 and possessed of a conchoidal fracture: its taste is burn- 

 ing and pungent, and its odour is that of wood snioke ; it 

 is fusible and readily inflammable. When kept melted in 

 an open vessel till it ceases to be fusible, it becomes more 

 and more brilliant, its fracuire passes to splinlerv, and it 

 assumes the perfect appearance of asphaltum. In propor- 

 tion as It approaches ihis slate it becomes less raid less so- 

 luble in alcohol, and at length scarcely gives a stain to this 

 menstruum. Naphtha has no action' cm it, and in this cir- 

 cumstance alone it diff'ers from asphaltum. 13r. M. then 

 proceeds to an examination of the Bitumens, and shows 

 that the diflTercnce between the products of recent vegetable 

 matter, and of the bitumens when subjected to distiflaiion, 

 consists in the former yielding empyreumatic acetic acid 

 and a black pitchy matter insoluble in naphtlia: while t!ie 

 latter aflord airnnonia and naphiha, bui litile or no acid, 

 lie then enters into a detailed inve3iigati(-n of the proper- 

 ties of -the very important class of Li^iiiUs, of those sub- 

 C g 3 stances, 



