116 Mr. Smithson on some Egyptian Colours. [Feb. 



their habits ; their ideas on many subjects. And products of 

 skill may likewise occur, either wholly unknown to us, or supe- 

 rior to those which now supply them. 



I received from Mr. Curtin, who travelled in Egypt with Mr. 

 Belzoni, a small fragment of the tomb of King Psammis. It was 

 sculptured in basso relievo which were painted. 



The colours were white, red, black, and blue. 



I have heard the white of Egyptian paintings extolled for its 

 brilliancy and preservation. I found the present to be neither 

 lead nor gypsum ; but carbonate of lime. Chlorides of barium 

 caused no turbidness in its solution. An entire sarcophagus of 

 arragonite proves that the ancient Egyptians were in possession 

 of an abundant store of this matter, remarkable often for its 

 perfect whiteness. Was it the material of their white paint ? 



The red was oxide of iron. By heating, it became black, and 

 returned on cooling to its original hue. In a case where so much 

 foreign admixture was present, since the layer of red was much 

 too thin to allow of its being isolated, I considered this as a bet- 

 ter proof of red oxide of iron than obtaining prussian blue. 



The black was pounded wood charcoal. After the carbonate 

 of lime with which it was mixed had been removed by an acid, 

 the texture of the larger particles was perfectly discernible with 

 a strong lens ; and in the fire it burned entirely away. 



The blue is what most deserves attention. Jt was a smalt, or 

 glass powder, so like our own, though a little paler, as to be 

 mistaken for it by judges to whom I showed it; but its tinging 

 matter was not cobalt, but copper. Melted with borax and tin, 

 the red oxide of copper immediately appeared. 



Many years ago I examined the blue glass with which was 

 painted a small figure of Isis, brought to me from Egypt by a 

 relation of mine, and found its colouring matter to be copper. 



I am informed that a fine blue glass cannot at present be 

 obtained by means of copper. What its advantages would be 

 above that from cobalt, it is for artists to decide. 



Intent upon the blue smalt, it unfortunately did not occur to 

 me to examine, till I had washed nearly the whole of it away to 

 waste, what was the glutinous matter which had been so true to 

 its office for no less a period than 3,500 years ; for the colours 

 were as firm on the stone as they can ever have been. 



A small quantity of it recovered from the water did not seem 

 to form a jelly on concentrating its solution ; or to produce a 

 precipitate with galls. I imagined its vegetable nature ascer- 

 tained by its ashes restoring the colour of reddened turnsol 

 paper, till I found those of glue do the same. 



The employment of powder of charcoal for a black would seem 

 to imply an unacquaintance with lamp-black, and, perhaps, with 

 bone black, and that of copper to colour glass blue, a deficiency 

 of cobalt. And if the glutinous matter should prove, on a future 

 examination, to be vegetable, our glue being then possessed may, 

 perhaps, be deemed questionable. 



