22:3 



only remark, that a much greater proportion of coal is obtained from 

 those substances by means of the above acid than can .be obtained 

 by distillation. 



Two experiments on the humid formation of coal are also de- 

 scribed : from one of these it appears that oak-wood may, by sul- 

 phuric acid, be converted into a coal which is very different from 

 charcoal, and which, by its mode of burning, and by its not affording 

 any alkali, resembles those mineral coals that do not contain bitu- 

 men. 



The other experiment shows that oak-wood may also be converted 

 into a sort of coal by muriatic acid ; but this coal retains some vege- 

 table characters, although no alkali can be obtained from its ashes. 



Mr. Hatchett now proceeds to make some remarks on the natural 

 formation of coal. After stating the various theories that have been 

 formed on that subject, he considers as the most probable the theory 

 which ascribes the principal origin of coal to vegetable substances ; 

 that idea of its origin being, he says, corroborated by the greater 

 number of geological facts. The observations, however, that have 

 been made upon the submerged wood found at Sutton and other 

 places, show, our author thinks, that vegetable substances, buried 

 under the sea or under the earth, are not, merely by such means, 

 converted even into the most imperfect sort of coal ; some other 

 process being evidently necessary to produce this change, which in 

 a former paper he endeavoured to demonstrate to be progressive. 



That some sorts of coal are of vegetable origin, there cannot, Mr. 

 Hatchett says, be any doubt : several of them, as the Bovey coal, 

 the Sussex coal, the surturbrand, &c. not only still retain some of 

 their external vegetable characters, but also yield resin, a substance 

 allowed to belong exclusively to organized natural bodies. Some 

 mineralogists, however, have attempted to distinguish the above- 

 mentioned coals from others, which they denominate True Mineral 

 Coals : but it has in the former part of this paper been shown, that 

 when pit-coal, Cannel-coal, and asphaltum, (which are considered as 

 of mineral origin,) are subjected to the action of nitric acid, and the 

 process is stopped at a proper period, there remains a substance 

 which is intermediate between resin and vegetable extractive matter. 

 It has also been stated, that, by similar means, a substance possessing 

 nearly the same properties may be obtained from the known vegetable 

 resins. 



Our author indeed admits that bitumen has never been formed by 

 any artificial process, and that he has himself attempted it, in various 

 ways, without success : yet we may conclude, from what has been 

 already said, that bitumen is a modification of the resinous and oily 

 parts of vegetables, produced by some process of nature, operated by 

 gradual means on immense masses ; and we have, he thinks, great 

 reason to conclude that the agent employed by nature in the forma- 

 tion of coal and bitumen is either the muriatic or the sulphuric acid. 

 Common salt, however, is never found in coal-mines, except when 

 they are in the vicinity of salt-springs ; whilst, on the contrary, py- 



