The above are the principal passages in the "Mappæ Clavicula," which supply deficiencies in most other books of Secreta; and I have translated them at length, both on account of the accuracy with which I have found the directions followed in ancient illuminated manuscripts, and because I believed that a knowledge of this ancient scale of colours might greatly facilitate accurate copying from old examples. I need scarcely say, that as the art of painting improved in Italy and the Netherlands, the illuminator's palette became enriched with several new and very brilliant colours;--such as the ultramarines and carmines (exceedingly scarce in early manuscripts) which make the books produced at Rome and in Northern Italy, during the 16th and 17th centuries, glow with a vivacity never previously attained. Every improvement made in one country was, however, speedily, communicated through these very art-treatises to other countries, and thus we find lakes and carmines freely used in England during the 15th century.[112] Ultramarine, indeed, forms the special subject of an essay by a Norman, comprised among the Le Bègue MSS. (already referred to), under the following title, which proves its novelty in Western Europe, at the beginning of the 15th century:-- "Anno 1411, Johannes de ... [illegible] Normannus de _Azurro novo_, lapidis lazulli ultramarini." The next collection of Secreta in importance, and probably in date to the "Mappæ Clavicula," is that of a Frenchman, Peter de St. Audemar. "With this treatise," observes Sir Charles Eastlake, "may be classed a similar one in the British Museum, written in the 14th century," but treating of a somewhat earlier practice in art. The identity of the colours for, and practice of, painters on wall and panel, and illuminators on vellum, is proved by the instructions to both being almost invariably given in the same books. Thus, the volume last mentioned commences--"Incipit tractatus de coloribus Illuminatorum _seu_ Pictorum"--as though there existed no practical distinction between the two. Another manuscript, of later date, also in the Le Bègue collection, exhibits, in its title even, a curious picture of the industry with which the Art of Illumination was studied in the principal countries of Europe,--introducing the student to a scribe, actually keeping a school at Milan. Thus, "Liber Johannis Acherius, A.D. 1398. Ut accessit a Jacobo Cona, Flamingo pictore:--Capitula de coloribus ad illuminandum libros ab eodem Archerio sive Alcherio, ut accessit ab Antonio de compendio illuminatore librorum in Parisiis et a Magistro Alberto Pozotto perfectissimo in omnibus modis scribendi, Mediolani scholas tenente."