Both these methods were used by the artists of the early period. Where the work is far from the eye, as in the clerestory windows, we usually find large single figures--far larger, often, than life--filling the whole window, like the big angel from Chartres on Plate X. and the smaller and older figure of Methuselah from Canterbury on Plate III. When, on the other hand, the work is near the eye, as in the aisle windows, they used the other method, filling each opening of the iron-work with a small subject-panel like that of Noah and the Dove in Plate IV., thus producing what is called the medallion window. [Sidenote: Medallion windows.] At first the lattice work consisted merely of upright and horizontal bars. These, it is true, sometimes, as in the twelfth century window at Poitiers in Plate II., were manipulated to fit the subject, but more usually the subject fitted the bars. [Sidenote: Bent iron-work.] In the earliest form of medallion window, such as those in west windows at Chartres and some of the earliest ones at Canterbury, the window is divided by the iron-work into a series of regular squares, each of which alternately is filled with a square and a circular figure-subject. Later, however, in the thirteenth century, the iron-work itself was bent into geometric patterns which the medallions were shaped to fit, producing the elaborate designs shown in the insets of the whole windows in Plates IV. and VIII. from Canterbury. Even when in the latter part of the thirteenth century there was a return, prompted no doubt by motives of economy, to iron-work composed of straight bars, the influence of these elaborate lattices is still seen in the shapes of the medallions, though these are no longer outlined by the iron-work which now passes across or between them. An example of this is shown in Plate XIV. from Rouen Cathedral. [Sidenote: The method of painting.] (4) _The Method of Painting._--This consists of vigorous line work in the brown enamel, laid on with a brush in beautiful, firm, expressive strokes on a ground of clear glass. Lettering and patterns are formed by being scratched out clear from a solid coat of enamel. There is no attempt at modelling in planes or at light and shade, and half-tone is only used, as I shall presently explain, to soften the edges of the line work. [Sidenote: Irradiation.] Now the optical law which most affects the technique of stained glass is that of which the effect is known as "irradiation." In an unscientific work it is enough to say that it is the law which causes the filament of an electric light, in reality thin as a hair, to appear when incandescent as thick as a piece of worsted. In the same way it makes the clear spaces of glass appear larger than they really are in proportion to the obscured parts, and also tends to make them look rounded.