Dr MacCiilloch mi Peat. SOS 
ly considered as an analysis, namely, the application of heat in 
close vessels, or destructive distillation. By conducting this 
process in the usual rude manner, there are obtained a set of 
new compounds, together with a portion of the elementary con- 
stituents fi’om which these compounds, and the original subject, 
are formed. With more care, a new set of compounds alone 
are obtained, and, in either case, these are again capable of be- 
ing subjected to a new analysis, so as to furnish, In a sufficient- 
ly accurate manner, the required information. It is unnecessa- 
ry for the purposes of this paper, to enter into any minute de- 
tails on this subject, but it will be sufficient to state, that by ex- 
amining the various nature and proportions of these compounds, 
as they are obtained from the different materials, or, if necessa- 
ry, by again decomposing them into their elements, the propor- 
tions of these elements, under different circumstances, may be 
obtained with sufficient accuracy for the objects in view. Thus 
the progress of change in the vegetable matter, may be traced 
by the gradation in these proportions during the progress of 
that change ; and thus also certain useful analogies may be dis- 
covered between peat under all its forms, and other compounds 
which differ from it rather in their mechanical than in their che- 
mical nature. 
If fresh vegetable matter, (and it is here most convenient to 
consider the ligneous substance), be subjected to distillation by a 
naked hre, certain volatile products are obtained, and char- 
coal remains behind. The chief of these volatile products are 
Tar a volatile oil, and acetic acid. A varying proportion of 
* I have given to this substance the name of Tar, because that name is so ap- 
plied! in the charcoal manufactories, where it is obtained in considerable quantity. 
The tar used for naval purposes, being always procured from fir by a similar pro- 
cess, is a compound of this substance and the turpentine of that tree. In the 
same manner the term of Pitch will here be applied to the solid material remain- 
ing after a gentle distillation of this tar ; nautical pitch being a compound of com- 
mon resin and this substance. The oil of turpentine, together with the oil of the 
wood, is separated in this latter case, as the oil of wood alone is in the former. I 
may here refer the reader to a paper in the second volume of the Geological 
Transactions, in which the subject has been examined in some detail with other 
views. 
The pitch, in a certain state of hardness, is the Bistre of artists, on which 
some remarks will also be found in the same paper. 
