en the Colours used in Painting hj the Ancients. 3j7 



There is much reason for supposing that this stained glr.ss, or 

 vuKog, was tinged with oxide of cobalt ; and that these colours 

 were simihir to our smalt. 1 have not for.nd any powdered co- 

 lour of this ki)id in the baths of Titus, or in any other Roman 

 ruins ; but a blue glass tin:j;ed with cobalt is very common in 

 those ruins, which wlien powdered forms a pale smalt. 



I have examined many partes and glasses that contain oxide 

 of copper ; they are all IjTueish green, green, or of an opacjue 

 watery blue. The transparent blue glass vessels whicli are found 

 with the vases in the tombs in Magna Gia^cia are tinged with 

 cobalt; and on analysing different ancient tvamparent blue glasses 

 which Mr. Millingen was so good as to give me, I found cobalt 

 in all of them*. 



Theophrastus, in speaking of the manufacture of glass, states 

 as a report that ";^«Xxi;" was used to give it a fine colour, and 

 it is extremely probable that the Greeks took cobalt for a 

 species of yjxK7iog. I have examined some Egyptian pastes 

 which are all tinged blue and green with copper ; but though I 

 have made experiments on nine diiiereiit specimens of ancient 

 Greek andUomun trniisparenl blue glass^ I have not found cop- 

 per in any, but cobalt in all of themf- 



V. Of the ancient Greens. 

 The ceiling of tlje chambers called the Br.'hs of Livia is highly 

 ornamented with gilding and paintings ; the larger paintii:g3 

 have been removed, but the ground-work and the borders re^ 

 main. A fragment detached fro!;i the borders, whi-jh appears 

 of the same cnlom- as the ground-work, v/as of a ^ecp sea green. 

 The colouring matter examined, proved to be soluble in acids 

 with effervescence; and when precipitated from acids, it redis- 

 solved in solution of ammonia, giving it the. bright bhje tint pro- 

 duced bv oxide of copper.^ There ^te several different shades of 

 green employed in the baths of Titus, and on the fragments found 

 near the momnnent of Caius Cestius: in the vase of mixed co- 

 lours I found three different varieties ; one, which approached 

 to olive, was the common green' earth of Verona; another, which 



* The mere fii'iion of thfise g!a=;ses vilh all;ali and diiifistion of the pro- 

 dint witli iiiiiii;uic acid whs siitfiri'iit to produce a sym[)ritliel!c ink tiom 

 tliein; even the silica separatpd liy the >ci(l ;i;a!ned a taint hltie {;rceii tint 

 by heat, and tlie sohition in niuiiauc acid Ijecanie perninnciitly f;rcen.Uy 

 the action of sulplniric acid, a ph.Enoinenon Dr. Marcct has observed as 

 belonging to tlie iiuiriatr of cohidt. 



t A gentleman at Milan inforuied nic last snmmor, tliat he had found 

 oxide of cohalt in the hlue [;!abs found i.ii the ruins of Ilaclrian's villa, and 

 at this time 1 had no idea that cobalt was knouii lo the iM'cicnts. Rlr. 

 llMichelt and .^Jr. Klapnnh had holh found <j\ide of copper in bonic aa- 

 citnt Llue glasses, which I coiicei* c niuit l;uve been opafiuc. 



2 3 was 



