Hartley — 0)i the Illuminations of the Book of Kells. 489 



Indicum purpurissimum — " From the statement of Pliny that, 

 when thrown upon hot coals, it gives out a beautiful purple flame, 

 this was obviously indigo." 



Purples. 



Purpurissimum was a high-priced pigment, made by putting a 

 kind of white clay into caldrons containing the ingredients for 

 dying purple : it was therefore a lake. The celebrated purple dye 

 of the Tyrians was obtained from a shell-fish, the murex or bucci- 

 num. Davy ascertained that the colouring matter of the ancient 

 purple examined by him was combustible ; the probability is very 

 great that it was a preparation of this character. Berthelot says, 

 however, that the ancients were undoubtedly aware that glass 

 could be coloured purple by means of gold, and that they appear 

 to have been not unacquainted with the purple of Cassius, which 

 is obtained from a solution of gold by the action of a solution 

 of tin. According to our knowledge of this substance, it appears 

 to have been discovered by Cassius of Leyden in the year 1683, 

 for the earliest description of its preparation we owe to him. In 

 Les Origines de I'Alchimie, p. 93, it is remarked that there appears 

 to have been an intimate connexion between the preparation of me- 

 tallic compounds and the process of dying purple. This is sugges- 

 tive of the probability that gold was used for the purpose. 



From the work attributed to Democritus, it is evident that several 

 purple colours were in use, namely, cochineal ; archil, obtained from 

 lichens ; garancine, from the madder root ; and likewise indigo. 

 The lilac tint in the "Book of Eells" was probably a lake prepared 

 from lichens. See Les Origines de I'Alchimie, pp. 350-361. 



As to the source of supply of these colours, one cannot other- 

 wise suppose than that, in the early days of the Christian era, and 

 still further back, the art of preparing colours was inseparable from 

 the art of painting, for even at the present day there are English 

 painters who can prepare their own colours, vehicles and varnishes, 

 and whose processes have been handed down to them by their masters. 

 The master who taught the art of designing and painting to the artist 

 who executed the " Book of Kells " unquestionably knew how to pre- 

 pare the colours. As for the materials, malachite, CuCOs'CuHgOa, 

 green in colour, is found near Cork and Limerick; chrysocoUa, 

 OuSi03'2H30, green to blue in colour, is found in the county Cork; 



