56 ^ LECTURE X. 



colours are employed, there is less difficulty in producing a uniformity of tint 

 than with water colours, each coat of the colour being laid on in sufficient 

 quantity to cover all that is below it without mixing: hence it becomes easier 

 to make any alterations that may be required. For water colours of all 

 descriptions, a certain quantity of gum is used, and sometimes a size made of 

 isinglass, with a little sugarcandy. Body colours contain less gum than other 

 water colours. Besides paper, wood, silk, and cotton velvet, are sometimes 

 used for drawings in water colours. 



In miniatures, the most delicate tints are laid on in points, with simple water 

 colours ; but for the draperies, body colours are sometimes used. They are 

 commonly executed on ivory. 



For painting in distemper, the colours are mixed with a size made by boil- 

 ing shreds of untanned leather, or of parchment, for several hours : this me- 

 thod is chiefly employed for colouring walls or paper, but sometimes for paint- 

 ing on cloth. For delicate purposes, the size may be made with isinglass. 



When a wall or cieling is painted in fresco, the rough coat of the plaster 

 is covered with a coat of fine sand and lime, as far as it can be painted before 

 it is dry, the colours being partly imbibed by this coat, and thus becoming 

 durable. When they have been once laid on, no alteration can be made, 

 without taking off the last coat of plaster, and each part must be completed 

 at once ; it is therefore always necessary to have a finished drawing for a 

 copy ; this is visually executed on paper, and is called a cartoon. The colours 

 can be only of earths or metallic oxids ; they are prepared as for painting in 

 distemper. The only paintings of the antients, which have been preserved, 

 were executed in fresco. 



The art of painting in oil was first discovered by Van Eyck of Bruges, to- 

 wards the end of the 14th century: it has now become almost the only man- 

 ner in which paintings of magnitude are performed. The colours are mixed 

 with linseed or nut oil, and sometimes with oil of poppy seed, together with 

 a small portion of oil of turpentine, to assist in drying them; and with the 

 occasianal addition of other oily and resinous substances. The work may be 

 fjxecuted on wood, cloth, silk, paper, marble, or metals: these substances 



