108 Experiments on a Substance which possesses 



phnric acid has probably been the principal agent, and that 

 by means of this acid the oils of the different species of wood 

 have been converted into bitumen, and a coaly substance has 

 beeti formed. 



The third opinion is that of Arduino, who conceives coal 

 to be entirely of a marine formation, and to have originated 

 from the fat and unctuous matter of the numerous tribes of 

 animals that inhabit the ocean. 



And the fourth is Mr. Kirwan's opinion, who considers 

 coal and bitumen to have been derived from the primordial 

 chaotic fluid *. 



The limits of this paper will not permit me to enter into 

 the various arguments and facts which have been adduced 

 in the support of these different opinions ; but the second, 

 or that which regards the vegetable substances as the prin- 

 cipal origin of coal, seems by much the most probable, be- 

 cause it is corroborated by the greater number of geological 

 as well as by many experimental results. Most of the former 

 have, however, been stated in different works, and I shall 

 therefore only notice a few of the latter which have occurred 

 in the course of my experiments. 



The observations of Dr. Correa de Serra on the wood of 

 the submarine forest at Sutton, on the coast of Lincoln- 

 shire, together with many similar accounts which have been 

 published in the Philosophical Transactions and other works, 

 demonstrate, in the most satisfactory manner, that whether 

 vegetables are totally or partially buried under the waves or 

 under the earth, they are not merely by such means con- 

 verted even into the most imperfect sort of coal f. Some 



process, 



• Geological Essays, p. 327. 



\ In my paper " On the Change of some of the proximate Principles of 

 Vegetables into Bitumen" I have quoted the remarks of Bergman, Von Troil, 

 and others, on the compressed state of the trunks of the trees which have 

 been converted into surturbrand, Bovey coal, and similar substances. The 

 same observation has been also made by Dr. Correa de Serra respecting the 

 timber of the submarine forest at Sutton ; and this is the more remarkable, as 

 the submerged vegetables at Sutton do not exhibit any appearance of carboni- 

 zation. 



Dr. Correa says, " In general the trunks, branches, and roots of the de^ 

 cayed trees were considerably flattened ; which is a phenomenon observed 



