231 



That jet is a pure bitumen, differing from amber, only in its having 

 undergone some process by which its colour has been changed, 

 will appear still more probable from the following relation of the 

 learned Dalecamp, 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 

 different 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 during 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 



* C. Plinii Secundi Historise Mundi, lib. xxxvii. Colonise Allobrogum, 1615. lib. 

 xxxvii. p. 733. 



