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Dalechamp, in his annotations on the Natural History of Pliny*. 
“ I have,” he says, “ a piece of jet, which, beyond all doubt, has 
been digested for many ages in the bowels of the earth. It was dug 
out of the quarries near Narbonne ; one half of it is black, and the 
other yellow, resembling amber.” 
Having ventured to assume that jet is bitumen changed by a 
particular process ; it may be expected, that as bitumen appears in 
diiferent forms, so should jet : — and this is the case. According to 
the form of the substance from which the bitumen derived its origin, 
will, frequently, be the form in which the jet appears. If the jet 
has proceeded from a piece of detached bitumen, which had at- 
tained a state of softness approaching even to fluidity, such as that 
in which amber must, at one period, have existed ; its surface, and 
the whole of its external form, will yield an appearance plainly 
declaratory of the very soft state in which it has existed. 
But should it have originally been wood, which dm'ing its bitu- 
minization had made but little approach to liquefaction, the fibrous 
texture of the wood may perhaps be still discernible. This, indeed, 
frequently happens ; and sometimes the external part will display, 
not merely the texture, but the general form, and even the colour, 
of wood. A specimen of this kind is depicted, Plate I. Fig. 4. 
On the flat surface of this specimen the fibrous texture of the wood 
appears exceedingly well marked ; whilst, at the end, the conchoidal 
fracture, the jet black, and the glassy lustre, sufficiently evince its 
bituminous nature. 
Jet has obtained a distinction, among collectors, into English or 
foreign ; they being guided, in making this distinction, merely by its 
weight. Thus that which swims on water they describe as English, 
but that which is heavier they suppose to be foreign. The grounds 
of this distinction are, that the pieces of jet found on the English 
* C. Plinii Secundi Historise Mundi, lib. xxxviL Colonise Allobrogum, 1615. p. 733. 
