346. In the patterns of tapestries and carpets, when the principal effects to be aimed at have been determined, it may be seen what points of ordinary painting may be sacrificed to obtain them, and what must be done for perfecting the _special portion of their imitation_. Beginning with the physical condition of the coloured elements the weaver employs, and the texture of the tapestry, we see the necessity of representing in this kind of work only large, well-defined objects, and especially such as are remarkable for the brilliancy of their colours. The patterns for hangings must recommend themselves more by the opposition of their colours than by the minute finish of their details. To pretend to rival painting in these manufactures is to establish a confusion most detrimental to the progress of arts, absolutely distinct from painting, both in their purpose and their means of execution. 347. The principles truly essential to these arts of imitation being once deduced from the peculiarities of each, it becomes easy to point out by what efforts we may hope to obtain true perfection. CHAPTER I. ON THE ELEMENTS OF GOBELINS TAPESTRY. 348. To make mixtures of coloured threads intelligently, we must be guided by the three following rules:—The first two resulting directly from observation of facts; the third being the natural deduction from the facts comprised in the two former. RULE I.—THE BINARY MIXTURE OF PRIMARY COLOURS. _When we unite Red with Yellow, Red with Blue, Yellow with Blue, the threads must not reflect a perceptible quantity of the third primary colour, if we would have Orange, Violet, and Green as brilliant as it is possible, by this method, to obtain._ EXAMPLE A.—_Red and Yellow._ Plate 11. 3 Red threads with 1 Yellow thread, 2 ” ” 1 ” ” 1 ” ” 1 ” ” 3 Yellow ” 1 Red ” 2 ” ” 1 ” ” yield mixtures which appear to the eye in proportion to the two colours mixed. There is no appearance of grey in any of these mixtures, when we employ a red more inclining to orange than to crimson, and a yellow more inclining to orange than to green. [Illustration: PLATE XI.] B.—_Red and Blue._ 3 Red threads with 1 Blue thread, 2 ” ” 1 ” ” 1 ” ” 1 ” ” 3 Blue ” 1 Red ” 2 ” ” 1 ” ” yield mixtures which appear to the eye in proportion to the two colours mixed. If we use a red and a blue inclining to violet, the mixture will contain no grey. C.—_Yellow and Blue._ 4 Blue threads with 1 Yellow thread, 3 ” ” 1 ” ” 2 ” ” 1 ” ” 1 ” ” 1 ” ” give mixtures which appear to the eye in the proportions of the two colours mixed. If we use yellow and a blue inclining to green more than to red, the mixture will contain little or no grey.