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LETTER XV. 
AMBER KNOWN TO THE EARLIEST WRITERS IN NATURAL HISTORY 
JET SUCCINUM NIGRUM OY THE ANCIENTS CANNEL COAL 
DIFFERENCE BETWEEN IT AND JET. 
Assuming that the substance treated of in this letter, is a bitu- 
minous substance, deriving its origin from the operations of a 
peculiar process on vegetable matters, which have been long buried 
in the earth, I shall introduce its history here, among those of the 
purer bitumens ; reserving the examination of the various opinions 
respecting its nature and origin, until I have endeavoured to point 
out the general principles on which, I presume, changes of this 
nature depend. 
Amber, the electrum of the ancients, is a bituminous, inflammable 
substance, of a yellow colour; varying in its shades of colour, as 
well as in its degree of transparency. Its fracture is conchoidal, 
and manifests a glassy lustre ; and it is susceptible of a fine polish. 
Its specific gravity is 1.0^8 to 1.085. By friction it yields a peculiar 
odour, and acquires the property, in a high degree, of attracting to 
it light substances. 
Amber appears to have been known to the earliest writers in 
natural history. Thales of Miletus was highly interested by its elec- 
tric property. Herodotus mentions the places where amber had 
been found ; and its peculiar qualities were well known to Aristotle 
and to Plato. Philemon classed it among fossils, and distinguished 
it into two kinds, the white and the yellow ; which, he relates, were 
taken out of two different mines in Scythia. Pliny*, who frequently 
* Lib. xxxvii. cap. 3. 
