[ 682 ] 
been changed, though the texture has remained en- 
tire enough to allow us to diftinguifh to what king- 
dom it belongs. — All bitumens, pifTafphaltum, pel- 
filaeum, &c. Teem to be no more than productions 
of refinous fubftances united with mineral acids, 
which have caught fire in the earth by fermenting 
with heterogeneous matter, and have thus under- 
gone a fort of natural diflillation and exaltation. 
Thefe are more than chimerical notions, and are 
even demonftrated by experiments ; for amber can 
be produced artificially, as likewife bitumens by the 
diflillation of refinous fubflances with mineral acids ; 
and there is great probability, that pit- coal might be 
imitated. I am, 
S I R, 
Brufleis, June 1 1, Your mod: obedient and 
1756. 
obliged humble fervant, 
Edward Wright. 
CVI. A RetraElation , by Mr. Benjamin Wil- 
fon, F. R. S. of his former Opinion , con- 
cerning the Explication of the Leyden Ex- 
periment. 
To the Royal Society. 
Gentlemen, 
Read June 24, nr Think it neceffary to retraCl an opi- 
J 75 6 - n j on concerning the explication of 
the Leyden experiment, which I troubled this Society 
with 
