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shores are thus light, whilst the handsomer specimens brought from 
France and Prussia are more ponderous : the fact, however, is, that 
the pieces of jet found on our shores are also chiefly foreign ; and, 
having been detached from the strata of the opposite shores, have, 
in consequence of their lightness, floated here on the waves of 
the sea. 
The transition of jet into cannel coal is frequently very difficult 
of detection ; the difference between the two substances seeming to 
depend entirely on the quantity of foreign earthy matters which have 
been introduced into the fluid bitumen. 
One mark of distinction between jet and cannel coal, perfectly 
accords with the opinion which I have offered respecting their 
formation. Jet, which is pure bituminized vegetable matter, some- 
times, as has been already remarked, displays not only the general 
form, but the texture and colour, of wood, manifesting that it is 
purely bituminized wood, some parts of which, and these generally 
the cortical, having resisted the influence of the fermentation more 
than that part which is more generally considered as wood. But in 
cannel coal, which has been in so fluid a state as to have admitted 
the intermixture of earthy matters, seldom any thing of this kind 
appears. Impressions of various vegetable substances are indeed 
often displayed on its surface, possessing such a degree of correct- 
ness and sharpness, as plainly to evince its having been in a very 
soft state when the impressing substance was applied to it; but 
these extend no deeper than the surface, its substance or texture 
seldom pointing out the substance from which it originated. Re- 
presentations of the appearances which thus offer themselves to our 
view you will see depicted, Plate I. Fig. 6 & 7- 
Yours, &c. 
