of some of the Principles of Vegetables into Bitumen , &c. 389 
circumstances, the process of carbonization, and formation of 
bitumen, has not taken place in the first instance, and as these 
effects have proceeded to the ultimate degree in the last, it seems 
most proper that we should seek for information, and for positive 
evidence, in the second example, which appears to be the mean 
point, exhibiting effects of natural operations, by which bitumen 
and coal have been imperfectly and partially formed, without 
the absolute obliteration of the original vegetable characters ; 
and, although I have selected the Bovey coal as an example, 
because it is found in this country, we must recollect that 
similar substances, or strata of bituminous wood, are found in 
many parts of our globe; so that the example which has been 
more immediately chosen, is neither rare nor partial.* 
The nature, however, of the various kinds of bituminous wood, 
may in some respects be different ; but this I have not as yet 
had the means of ascertaining ; I shall therefore only state the 
facts resulting from experiments made on Bovey coal, and more 
especially on a peculiar bituminous substance with which it is 
accompanied. But, before I enter into these particulars, it will 
be proper to mention a very remarkable schistus, with which 
I was, some months since, favoured by the Right Hon. Sir 
Joseph Banks. 
• Strata of bituminous wood are found in various parts of France, in the vicinity of 
Cologne, in Hesse, Bohemia, Saxony, Italy, and especially in Iceland, where it is 
known under the name of Surturbrand. 
