Earthen Vases known by the Name of Etruscan. 61 
cup, detonation takes place. Sparks are seen, which are always 
renewed ; — a phenomenon which is long observed, when the 
combustible particles are much enveloped in those of the clay ; — * 
a circumstance which causes the combustion to go on slowly. 
If any acid be mixed with the salt left by this detonation, car- 
bonic acid gas is produced by effervescence. 4. In muriatic and 
nitric acid, the black particles of the mass do not undergo any 
change. 
From these experiments it may be inferred, that the black 
pigment in the mass of these vases, is a combustible substance, 
and, in fact, either carbonaceous or bituminous. 
From these experiments I proceeded to others, the object of 
which was, to produce a substance similar to the black mass of 
the antique vases ; and in this I succeeded. I made use of the 
same substance which I had applied to the making of varnish, 
namely, Asphaltum ; and of that remarkable variety coming 
from the Dead Sea, which was already known to the ancients. 
Of this, reduced to powder, I added to some of the clay used 
in the manufacture of tobacco-pipes and stone-ware, intimately 
mixing with them a sufficient quantity, to convert the white co- 
lour of the clay into grey. Of this mass I formed cylinders, 
which I dried in the air, and smoothed at the surface. I gra- 
dually heated these cylinders in a crucible placed among burn- 
ing embers, to the degree at which asphaltus is melted. In this 
manner the clay was thoroughly penetrated by the liquid as- 
phaltus becoming perfectly black, and, at the same time, the 
surface of the cylinders became of a shining smoothness, as if 
varnish had been applied to it. The mass of these cylinders 
agreed perfectly in every respect with the black substance of the 
Grecian and Etruscan vases. 
This, then, being the case, and since the black varnish of the 
painted Grecian vases is intimately connected with the substance 
which gives the colour in the vases which are entirely black ; 
and as the black vases have, without doubt, been manufactured 
in the same places with the painted ones, it becomes probable, 
that the problematical black varnish of the painted vases, also 
has been produced in the manner above described, or in one 
very similar to it. 
The examination of the black vases of Grecian and Etruscan 
