1815.] Transactions of the Geological Sbciety, Vol. II. 445 



When wood is exposed to destructive distillation there comes over 

 a thick black fluid like tar. Great quantities of this substance are 

 obtained at the powder works from the distillation of willow and 

 alder. It was this substance that Dr. MaccuUoch examined. It 

 is very inflammable, and may be burnt like oil in a lamp. When 

 it is washed in water, that liquid separates a considerable propor- 

 tion of acetic acid, coloured by an oily matter, which has an 

 empyreumaiic smell and taste. When triturated, or boiled with 

 carbonate of potash, it acquires a pitchy consistence; but does not 

 seem to combine fully with the alkali. It is soluble in alcohol, 

 ether, caustic fixed alkaline lees, acetic acid, and the mineral 

 acids. Fat oils and fresh essential oils dissolve it imperfectly ; but 

 the drying oils and inspissated essential oils act on it more readily. 

 Coloured oil of turpentine dissolves a good deal of it. Naphtha 

 has scarcely any action on it. When exposed to a heat just suffi- 

 cient to Keep it boiling, an oil comes over, at first light coloured, 

 but becoming d;irker as the process advances. If the heat of the 

 retort be gradually increased to redness, nothing remains but a 

 spongy charcoal. There is found in the receiver an oil and acetic 

 acid, combined with a little ammonia. No gas is evolved in this 

 process, if the heat be carefully managed. When a gas is formed, 

 the oil has been exposed to too high a temperature, by letting the 

 fire act too much on the upper part of the retort. If the heat be 

 continued for a certain time, what remains in the retort resembles 

 petroleum ; if longer, maltha ; if longer, bitumen ; and if still 

 longer, only coal remains. But these resemblances are merely ex- 

 ternal. Bitumen and our substance are different in their compo- 

 sition ; since the first is soluble in naphta, the second inspluble. 

 Dr. MaccuUoch conceives it probable that vegetables may have 

 been convertt d into bitumen or jet, by the action ol water, and 

 the bitumen afterwards converted into coal by heat. He shows 

 that heat is incapable of bituminizing wood, but that it converts 

 jet into coal. Many other very ingenious hypotheses respecting 

 the origin of the various species of coal and plumbago occur in 

 tliis paper ; but they are of so bold a nature, and so little supported 

 by the present state of our knowledge, that 1 am afraid to enter 

 upon tliem, lea-t they should lead to a tedious controversy about a 

 subject, the decision of which is at present obviously beyond the 

 reach of our facuiiie*. The valuable part of the paper is the che- 

 mical description of the new substance obtained by distilling 

 vegetables, which Dr. M. proposes to distinguish by the name of 

 lislre, 



11. Mineralogicul Account of the Lie of Man. By I. F. Berger, 

 M. D. M.G. S.— The Isle of Man, the situation of which is too 

 well known to require specification here, is rather more than 30 

 miles lung fro;n north to soitli, while its breadth varies from 15 to 

 eight miles. The northern t.xtreniiiy is tolcihbly low for about 

 five miles, where a range of mountains commence that proceed to 

 the southern extrcjnity. This group of mountains consists of three 



