Bricks are laid in mortar, and this makes a wall one solid mass and stronger than it could be without any cement. But mortar does more than this. It is more elastic than brick, and therefore, when a wall settles, the mortar yields a little, and this often prevents the bricks from cracking. Bricks are always thirsty, and if one is laid in mortar, it will suck the moisture out of it almost as a sponge will suck up water. The mortar thus has no chance to set, and so is not strong as it should be. That is why the bricklayer wets his bricks, especially in summer, before he puts them in place. Lime or cement mortar will not set in freezing weather, and a brick building put up in the winter is in danger of tumbling down when the warm days of spring arrive. This thirstiness of bricks is their greatest fault. Three or four days of driving rain will sometimes wet through a brick wall two feet thick, crumbling the plaster and spoiling the wallpaper. That is why it is a poor plan to plaster directly on the brick wall of a house. "Furring" strips, as they are called, or narrow strips of wood, should be fastened on first and the laths nailed to these, or the wall can be painted or oiled on the outside. The best way, however, though more expensive, is to build the wall double. Then there is air between the two thicknesses of brick. Air is a poor conductor of heat; so in summer it keeps the heat out, and in winter it keeps it in. But brick will suck up water from the ground as well as from a storm; and therefore, when a brick house is to be built in a wet place, there ought to be a three-eighths-inch layer of something waterproof, like asphalt and coal tar, put on top of one of the layers of brickwork to prevent the moisture from creeping up. Bricks have their faults, but they will not burn, and when properly used, they make a most comfortable and enduring house. V AT THE GOLD DIGGINGS When gold was first discovered in California, in 1848, people from all over the world made a frantic rush to get there, every one of them hoping that he would be lucky enough to make his fortune, and fearing lest the precious metal should be gone before he could even begin to dig. The gold that these men gathered came from what were called "placers"; that is, masses of gravel and sand along the beds of mountain streams. Each miner had a pan of tin or iron, which he filled half-full of the gravel, or "pay dirt," as the miners called it. Then, holding it under water, he shook off the stones and mud over the side of the pan, leaving grains of gold mixed with black sand at the bottom. This black sand was iron, and after a while the miners removed it with a magnet, dried what remained, and blew away the dust, leaving only the grains of gold.