ON the right hand of the accompanying illustration are given two sketches of a modern roof, one slated and the other tiled. The figures on the left show that this formation has been anticipated by Nature, in the wonderful system of scales which cover the wings of butterflies and moths, and to which all their brilliancy of colour is owing. In spite of their minute size, most being too small to be distinguished by the unaided eye, they are arranged as regularly as the best workman could lay the slates or tiles on a roof, and on exactly the same principle. The shapes of these scales vary in almost every species, but they are always arranged on the same plan, namely, being placed in successive rows, each overlapping the other. In consequence, it is almost impossible to wet a butterfly’s wing with water. The insect may be plunged beneath the surface, and the long hairs of the body will be soaked and cling together in a very miserable fashion. But the water rolls off the wings like rain off a slated roof, and even if a few drops remain on the surface, they can be shaken off, and the wing will be perfectly dry. Mostly these scales are flat, but sometimes they are curved. I have among my microscopic objects a piece of wing from a South American butterfly, the scales of which are oblong and bent, just like the curved tiles shown in the second right-hand figure of the illustration. These beautiful scales are deep azure or warm brown, according to the direction of the light. Perhaps my readers may call to mind that some architects dislike the flat, square form in which slates are usually put on roofs, and try to make them less formal. [Illustration: SHELL OF TORTOISE.] [Illustration: HEXAGONALLY TILED ROOF.] Sometimes they take their square slates, and fit them with one of the angles uppermost, so that each slate looks something like the ace of diamonds in a pack of cards. Sometimes they are still more ambitious, and certainly succeed in producing a better effect, by cutting the slates in hexagons instead of squares, and fixing them as shown in the right-hand figure of the illustration. Putting aside the familiar hexagons of the honeycomb, and the apparent hexagons of an insect’s compound eye, we have in the common Tortoise an example of hexagonal plates that exactly resembles the slate roofing. In the next illustration we have a variety of the same principle exhibited in differently shaped tiles and scales. The figures on the right hand show the pointed, the square, and the oblong tiles. These also would answer very well as representations of different forms of scale armour, the one being intended to throw off rain, and the other to repel weapons.