12 



by the name of minium to the Romans, who called our modern mi- 

 nium by the name of cerussa usta, in consequence of the mode of 

 making it ; which, on the authority of Pliny, is said to have been 

 suggested by the accidental effects of a fire at the Piraeus at Athens, 

 by which ceruse was found converted into minium. 



From the description which Pliny gives of an inferior sort of ver- 

 milion, formed by calcining certain stones found in veins of lead, 

 the author is of opinion, that the mineral thus treated must have 

 been a natural carbonate of lead, which becomes red when burned. 



Among the yellows examined by Sir Humphry Davy, were ochres 

 of various tints, from being mixed with different quantities of chalk, 

 and the yellow oxide of lead or massicot. 



But though we have the evidence of Vitruvius that orpiment was 

 known to the ancients, and of Pliny that a substance nearly allied 

 to orpiment, termed Sandarach, was used by the Romans, the author 

 has not been able to detect either of these sulphurets of arsenic in 

 any of the ancient fresco paintings. 



Among some rubbish collected in one of the chambers of the baths 

 of Titus were several large lumps of a deep blue frit, which, upon 

 being analysed, were found to consist of soda, silica, and oxide of 

 copper. Upon examination of the different tints of blue observable 

 in the paintings of the baths, as well as several blues in fragments 

 of fresco painting from the ruins near the monument of Caius Ces- 

 tius, and from excavations made at Pompeii, it appeared that they 

 all consisted of the same blue frit, more or less diluted by admixture 

 with carbonate of lime. There appears to the author every reason 

 to believe this to be the colour described by Theophrastus, as disco- 

 vered by an Egyptian king, and anciently manufactured at Alexan- 

 dria. Vitruvius also speaks of the same colour under the name of 

 caeruleum, made in his time at Puzzuoli, by heating together sand, 

 flores nitri or natron, and filings of copper. 



Though Pliny and Vitruvius speak of Indian blue, which appears 

 to have been indigo, the author has not been able to discover any 

 remains of it at this time ; nor indeed of any other blue, excepting 

 the frit before mentioned among the opake blues used by painters. But 

 it is by no means uncommon to find among the ruins fragments of 

 transparent blue glass, which are tinged with cobalt ; and it would 

 appear, from a passage in Theophrastus, that the Greeks considered 

 cobalt as a species of ^a\Kos, in consequence of its property of giving 

 this blue colour. 



Among the several shades of green observable in the baths of 

 Livia, the baths of Titus, and elsewhere, the greater part are coloured 

 by carbonate of copper ; but one of them, which approached the olive, 

 proved to be the common green earth of Verona. It seems not impro- 

 bable that some of the greens which are now found in the state of 

 carbonate of copper may have been originally laid on as acetates; for 

 it appears from Theophrastus that the ancients were well acquainted 

 with verdigris. 



The only trace of any thing approaching to the ancient purple 



