on the colours used in painting by the Ancients. 1 09 
found with the vases in the tombs in Magna Graecia are tinged 
with cobalt, and on analyzing different ancient transparent 
blue glasses which Mr. Millingen was so good as to give 
iTie, I found cobalt in all of them.* 
Theophrastus, in speaking of the manufacture of glass, 
states as a report that “ x^Kog” was used to give it a fine colour, 
and it is extremely probable, that the Greeks took cobalt for 
a species of % u \ Kog . I have examined some Egyptian pastes 
which are all tinged blue and green with copper, but though 
I have made experiments on nine different specimens of ancient 
Greek and Roman transparent blue glass, I have not found 
copper in any, but cobalt in all of them.-f 
V. Of the ancient greens. 
The ceiling of the chambers called the Baths of Livia is 
highly ornamented with gilding and paintings ; the larger 
paintings have been removed, but the ground work and the 
borders remain. A fragment detached from the borders, 
which appears of the same colour as the ground work, was of 
a deep sea green. The colouring matter examined, proved to 
be soluble in acids with effervescence, and when precipitated 
from acids, it redissolved in solution of ammonia, giving it the 
# The mere fusion of these glasses with alkali and digestion of the product with 
muriatic acid was sufficient to produce a sympathetic ink from them; even the silica 
separated by the acid gained a faint blue green tint by heat, and the solution in mu* 
riatic acid became parmanently green by the action of sulphuric acid, a phenomenon 
Dr. Mar get has observed as belonging to the muriate of cobalt. 
f A gentleman at Milan informed me last summer that he had found oxide of co- 
balt in the blue glass found in the ruins of Hadrian’s villa, and at this time I had no 
idea that cobalt was known to the ancients. Mr. Hatchett, and Mr. Kiaprot-h 
had both found oxide of copper in some ancient blue glasses, which I conceive must 
have been opaque. 
