85 
from the myriads of insects which had fed on the vegetables. From 
the resolution of animal and even vegetable matter, in subterranean 
situations, may also have proceeded the phosphorus found in various 
metallic and other phosphates, so eminent in their brilliance and 
colours. 
« 
Yours, &c. 
LETTER X. 
PEAT OR TURF DESCRIPTION OF VARIOUS KINDS LENGTH OF 
TIME KNOWN FOUND IN VARIOUS PARTS OF THE WORLD. 
T HE substance, to which I next wish particularly to attract your 
attention, is one which has been seldom considered in relation to 
the bodies termed petrifactions ; but which, I suspect, is very nearly 
connected with those which derive their origin from the vegetable 
kingdom. Indeed, I shall endeavour to prove to you, that most of 
these bodies which have obtained so considerable an alienation from 
their original nature, have first passed through an intermediate state ; 
resembling that, in which the substance which is the subject of our 
immediate inquiry, is always found to exist. 
The substance here alluded to, is peat or turf ; well known to the 
inhabitants of most lowland countries, for the advantages it affords 
them by its combustible quality. It is found in various parts of the 
world, forming immense tracks, at various depths. It is a soft but 
compact substance ; its colour being of a bright reddish brown. As 
