This fact is, perhaps, greatly owing to the influence of climate. In the parts of the world which have been mentioned in connection with this subject, light and heat appear to be rather enemies than friends, and the object of the architect was to enable the inhabitants of his houses to avoid rather than to welcome both. Consequently, the Windows were comparatively insignificant. They were not needed for the purposes of light or air, those being generally furnished by the aperture in the roof, and consequently were kept out of sight as much as possible. But when architects had to build for a sterner, a colder, and a darker clime, where the sun never assumed that almost devouring heat and light which in hot countries drive the inhabitants to invent endless devices for obtaining coolness and shade, a different style of Architecture sprang up. In this the Window became nearly the most prominent part of the building: the elements were excluded by glass instead of stone, and the principal modifications of light were obtained by staining the glass in various rich colours. Perhaps the Window has attained its culminating point in the Crystal Palace, which is all window except its foundations. Partly in order to enable the glass to be inserted, and partly to increase the beauty of the building, and to avoid the mean appearance of Windows filled in with plain iron bars crossing each other at right angles, the interior of the Windows was adorned with stone “tracery,” varying much according to the epoch of the building. [Illustration: CADDIS GRATING.] [Illustration: WHEEL-WINDOW.] One of the most beautiful forms of the Window is that which is called the Wheel. The window itself is circular, and the tracery is disposed so as to bear an exact resemblance to an ornamental wheel, the lines of the tracery running from the circumference to the centre, just like the spokes of a wheel. One of these Wheel-windows is shown on the right hand of the illustration. On the other side is an object, which at a hasty glance might be taken for another Window of the same character. It is, however, the work of an insect, and not of man, and is magnified in order to show its structure better. Any of my readers who may happen to be entomologists or anglers, or both, are familiar with the Caddis-worm of our fresh waters. Most of us know that the Caddis is the grub or larva of the Stone-fly (_Phryganea_), an insect haunting the waterside, and so moth-like in its general aspect that many persons think that it is really a brown moth. The changes or metamorphoses of these insects are well worthy of notice.