If the architect is desirous to introduce into his ornament a natural object, such as a leaf, he may first try the effect which it will produce when applied in its natural state to the instrument, and he may then carve either the whole or the half of it in stone, and then examine what will be its final effect. If one half of the leaf is an inverted image of the other half, it is necessary only to carve one half of it, and place the reflectors at an angle contained as many times in a circle as twice the number of times that he wishes the whole leaf to be multiplied: for example, if the whole leaf is to be multiplied six times, the angle of the mirrors must be ¹/₁₂th of 360°, or 30°. The very same effect would be obtained by applying the whole leaf to the instrument when the inclination of the reflectors is 60°, or ⅙th of 360°. But when the whole leaf is not symmetrical in itself, or consists of two dissimilar halves, it must be applied in its entire state to the instrument. In the formation of circular Gothic windows, the architect will find the Kaleidoscope a most important auxiliary. By applying it to a mullion drawn upon paper, with a portion of the curves which he wishes to introduce, or by placing it upon various ornamental parts of the drawing of a Gothic cathedral, he will obtain combinations to which he has never observed the slightest approximation. In designing the decorations for ceilings, which are generally made of plaster of Paris, the same method should be followed as that which we have described for architectural ornaments. 2. _Ornamental Painting._ In ornaments carved out of stone or marble, or formed from plaster of Paris, the idea of colour does not enter into the consideration of the architect. The forms, however, which are necessary in ornamental painting, are always associated with colour; and therefore, in the invention and selection of these forms, the Kaleidoscope performs a double task. While it creates the outline, it at the same time fills it up with colour; and by representing the effect of the two in a state of combination, it enables the artist to judge of the harmony of his tints, as well as of the proportion of his forms.