120 Mr. Hatchett’s Experiments on a Substance, 
to a certain degree, and may be formed by the humid as well 
as by the dry way. 
Examples have been already stated respecting operations 
in which sulphuric acid has produced this effect, but the 
same likewise appears to be produced with some modifica- 
tions, whenever vegetable matter undergoes the putrefactive 
process ; for when this takes place, as in dunghills, &c. a 
large proportion of the carbon of the original vegetable sub- 
stances appears to be combined with oxygen sufficient to 
communicate to it many of the properties of coal, whilst the 
compound nevertheless is capable of being dissolved by water 
with the most perfect facility. 
It must not however be understood that by this process all 
the other elementary principles are separated, so that only 
the carbon remains combined with oxygen, but merely, that 
the other principles are so far diminished, that these, namely, 
carbon and oxygen, predominate in a state approaching to 
coal, although soluble in water. 
Such solutions, I have every reason to believe, are nearly 
similar to those afforded by vegetable substances which have 
been previously roasted, and although I have examined but a 
few of them, yet I shall relate some experiments which I 
have lately made on the peels of walnuts. 
It is well known that when these are kept in small heaps 
for a short time, they become soft, and break down into a 
black mass, which affords a brownish-black liquor. On these 
I therefore made the following experiments : 
1. 
About one ounce of walnut peels, which were become soft 
and black, was digested in water. 
A dark brown liquor was thus formed, and being filtrated, 
