144 Mr. Hatchett’s Experiments on a Substance , 
and considering the importance of the latter, it will not appear 
surprising, that it should immediately have engaged the prin- 
cipal part of my attention. 
In addition to the experiments which have been related in 
the three Papers upon this subject, I intended to have decom- 
posed the different varieties, to have compared their gases 
and other products with those of the natural substance called 
Tannin, and especially to have endeavoured to discover more 
economical methods of obtaining the artificial product ; for, 
exclusive of speculative science, this appears to be an object 
of consequence, not only respecting that useful and valuable 
branch of manufacture to which it immediately relates, but 
also as the means of preventing, or at least of diminishing, 
the premature destruction of timber in a country, where, on 
account of its population, as well as on account of its maritime 
not solve the grand geological problem, they must even, in an insulated point of 
view, be allowed to have opened a new and unexplored field of research in chemistry 
as well as in geology. 
In the 8 th section of this valuable Paper, the author has given an account of some 
experiments made on leather, horn, and fir sawdust, from which he obtained coal 
which burned with flame, and which apparently resembled some of the mineral coals. 
In one case also, he obtained a substance, which in external characters appeared 
somewhat similar to the mixture of asphaltum and resin found at Bovey, to which I 
have given the name of Retin-asphaltum. These experiments Sir James Hall 
intends to resume, and it is my earnest wish that he would do so ; for although I am 
strongly inclined to believe that the mineral coals have generally, if not always, been 
formed by some humid process, yet it is impossible to foresee the results which may 
be obtained from animal and vegetable bodies subjected to the effects of heat modi- 
fied by compression, as the principles of these bodies may be acted upon, and may be 
made to re-act on each other, under circumstances which until now have not been 
imagined. 
