1 36 Mr. Hatchett’s Experiments on a Substance , 
The second and most prevailing opinion is, that mineral coal 
is of vegetable origin, that the vegetable bodies have, subse- 
quent to their being buried under vast strata of earth, been mi- 
neralized by some unknown process, of which, sulphuric acid 
has probably been the principal agent, and that by means of this 
acid, the oils of the different species of wood have been con- 
verted into bitumen, and a coaly substance has been formed. 
The third opinion is that of Arduino ; who conceives coal 
to be entirely of 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 principal origin 
of coal, seems by much the most probable, because it is cor- 
roborated by the greater number of geological facts, 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 Lincolnshire, 
together with many similar accounts which have been pub- 
lished in the Philosophical Transactions and other works, 
demonstrate in the most satisfactory manner, that whether 
• Geological Essays, p. 327, 
