the exact scale of the window as it was to be, was composed of all the pieces cut out and numbered according to the various colours; and the third, also of the projected size of the window, was kept complete, to serve as a pattern in case the window should suffer any accident, and require to be restored or mended. Not one of these cartoons is known to be preserved to-day, but Rico y Sinobas points out that from the strong and simple character of their colouring and outline, the illuminated illustrations of Spanish thirteenth century manuscripts, such as the _Cantigas_, and the _Book of Chess_ of Alfonso the Learned, may well have been utilized for, or else be copied from, glass windows of that period. As soon as the cartoon was finished, the window-painter traced it upon the surface of the glass. This was in square pieces, fitted conveniently together, with sufficient space between the pieces to allow the passage of the leads. Before being laid upon the glass and being submitted to the fixing action of fire, the colours were mixed with honey, urine, vinegar, and other fluids or substances which served as mediums to attach the colour to the glass. Thus prepared, and in the form of powder, the colours were allowed to dry for two or three days before the glass was placed in the oven. Yellow, which was the strongest colour, and that which penetrated deepest beneath the surface of the glass, was made from certain combinations of silver and nitrate of potash, while oxides or other forms of copper, lead, iron, tin, silver, and manganese, were used for making black, white, red, green, blue, purple, violet, or flesh-colour. These colours penetrated the glass to the depth of about half a millimetre; but sometimes, after the colour had been applied, the craftsman would submit the glass to friction by a wooden polisher or wheel, thus giving it an appearance of greater clearness and transparency at any spot he might desire.