368. The coloured windows of a large church may be regarded as real, transparent tapestries, intended to transmit light, and to ally themselves harmoniously with the sculptures on the exterior, which destroy the monotony of the high walls of the edifice, and with the different monuments of the interior, among which tapestries must be taken into account. 369. My ideas on the employment of stained glass for windows may be summed up in the following terms:— 1. They produce their utmost effect only in the rose windows, bay windows, or pointed windows of large Gothic churches. 2. Only when they present the strongest harmonies of contrast, not of colourless transparent glass with the black produced by the opacity of the walls, iron bars, and strips of lead, but of this black with the intense tones of red, blue, orange, violet, and yellow. 3. Their designs must always be as simple as possible, and admit of the harmonies of contrast. 4. While admiring painted windows, of which a large number consist of paintings of undoubted merit, especially in regard to the difficulties overcome, I confess that it is a kind of painting which should not be much encouraged, because it never has the merit of a picture properly so called, it is more costly, and will produce less effect in a large church than a stained window of much lower price. 5. Windows of a pale grey ground, with light arabesques, have a very poor effect wherever they are placed. See the relations of the law of contrast with the decoration of the interiors of churches. THIRD DIVISION. _Colour Printing._ ON CALICO-PRINTING, AND PRINTING PAPER-HANGINGS. 370. I propose to examine only the optical, not the chemical, effects produced by patterns printed upon woven fabrics. Printing on textile fabrics was for a long time limited, so to speak, to cotton cloths. It is only of late years that it has been extended to fabrics of silk and wool, for furniture and clothing. This branch of industry has now undergone an immense extension, fashion having accepted these products with extreme favour; but, whatever may be the importance of the subject, in a commercial point of view, I must treat it briefly. This book is not directed exclusively to that branch of inquiry, and as all the preceding part is intimately connected with it, I shall merely state some facts which show, that, in ignorance of the law of contrast, the manufacturers and printers of cotton, woollen, and silk stuffs are constantly exposed to error in judging the value of recipes or colours, or as to the true tint of the design applied upon grounds of a different colour. FALSE JUDGMENT OF THE VALUE OF RECIPES FOR COLOURING COMPOSITIONS.