The Third lasts down to the end of the fifteenth century, by which time the influence of the classic Renaissance began to be felt in glasswork, but lingers on in belated examples well into the sixteenth. Between each of these periods there is a very short transitional period lasting hardly a decade, and occupying the closing years of each century. It must not be thought, however, that at any time design in stained glass stood still. Its history is rather one of periodic impulses, due no doubt to the work of individual genius, followed in each case by a long and gradual decline, towards the end of which artists began to grow restless and feel about for new modes of expression, and so prepare the way for the next impulse of genius. [Sidenote: The First Period.] The broad characteristics then which distinguish the First Period are-- (1) Its rich colour. (2) Its mosaic character. (3) The importance of the iron-work and its influence on the design. (4) The method of painting. * * * * * [Illustration: PLATE V THE ENTOMBMENT, FROM THE EAST WINDOW, CANTERBURY Twelfth or early Thirteenth Century] [Sidenote: Its rich colour.] (1) _Its Colour._--The colour of the glass in this First Period is of a barbaric richness, unequalled in the succeeding periods. A very deep and splendid blue is used, in contrast with the greyish-blue of later glass, and it is of an uneven tint, which greatly adds to its quality. The ruby,[5] too, is often of a streaky character and of great beauty. These two usually form the dominant colours in the window, the greens, yellows, and purples being used rather to relieve them. So much is the artist in love with his deep reds and blues, which he nearly always uses for the backgrounds of his figures, that he seldom insults them by painting on them except in so far as is necessary to the drawing, reserving his enamel mainly for the decoration of his whites and paler colours, keeping them in their places by a delicate fret of line and pattern work. It is only towards the latter part of the period, when the quality of the glass began to fail a little, that he ever covered the whole surface of a blue background with an enamelled diaper, to give it a depth and richness which was lacking in the glass itself. Except in the grisaille windows to be described later, in which a definitely white effect is aimed at, the amount of colour used in proportion to the white glass is considerably greater than in succeeding periods. Nevertheless the white is always present, running everywhere among the colour like a silver thread, relieving and beautifying it. In fact it was not till modern times that any glass-worker ever thought he could do without it. [Sidenote: Its mosaic character.]