The Wall and its Materials.--Bricks as they are and might be.--Trade Unionism.--Double Walls and their Uses.--Double Clothing.--The Refrigerator.--Cooking Vessels.--Fire-proof Safes.--Cocoon of the Silkworm, and its treble Walls.--Nest of the Little Ermine, Processionary, Gold-tailed, and Brown-tailed Moths.--Mud Walls.--Nests of the Termite.--Porches, Eaves, and Windows.--Nests of the Myrapetra and an Indian Ant.--The Sociable Weaver-bird and its Nest.--Thatching.--Arms of the Orang-outan.--Japanese and Chinese Rain-cloaks.--Eggs of the Gold-tailed Moth.--Action of Fur.--Slates and Tiles.--Scales of Butterfly’s Wing.--Shell of Tortoise.--Scales of Manis, Fish, and Armadillo. We now come to the Walls of the house, in which there is more variety than might be imagined. Take, for example, our modern houses of the “villa” type. They are nothing but the merest shells, made of the flimsiest imaginable materials. Some years ago, while walking through a suburb where some very showy houses were being built, I amused myself by going over them and testing them. There was scarcely a room in which I could not thrust an ordinary walking-stick through the wall. When they were “finished” and “pointed,” the houses looked beautiful, but their heat in summer, cold in winter, and moisture in wet weather, can easily be imagined, especially as the sand with which the mortar was mixed had been procured from the banks of a tidal river. There is not the least necessity for such buildings. It is absurd to run up such edifices as that, and then charge £120 per annum for rent. The whole system is as rotten as the houses, and there is nothing but prejudice and trade-unionism to prevent our houses being cool in summer, warm in winter, and dry in all weathers. It is well known that air is practically a non-conductor of heat, and that therefore a layer of air between two very slight walls is just as warm as if the wall had been made of solid stone. Now, there are several inventions whereby the present brick could be made half its present weight, twice its present strength, hard and smooth as earthenware, so that it could not absorb water like our common brick, and pierced with holes through which air could pass. [Illustration: FUR.] [Illustration: NEST OF LITTLE ERMINE-MOTH.] [Illustration: ICE-HOUSE.] Unfortunately, however, there is a stringent rule among brickmakers and bricklayers that they are to play into each other’s hands, and that no bricklayer is to touch a brick which has not been made in some definite district. Should he do so, he is a marked man, and will stand but little chance of getting even a day’s work.