By a play of affinities, which those who are at all acquainted with chemistry will be at no loss to comprehend, a degree of action and re-action takes place among the ingredients, and between them and the iron surfaces, which at last causes the whole to unite as one mass. In fact, after a time, the mixture and the surfaces of the flanches become a species of pyrites (holding a very large proportion of iron,) all the parts of which cohere strongly together. The inner parts of the faucet ought to be no larger in diameter than just to fit the spigot. This supports the pipe, independently of the cement, and prevents the risk of hurting the joint from any external stress. The inner faucet is commonly made about 2½ inches deep, and has the spigot inserted 1½ inch into it. The practice of some workmen, is to make the outer faucet, or that which contains the cement, six inches deep, for all pipes above six inches diameter; and to make the faucets of all pipes below six inches, the same depth as the diameter of the pipes. It is usual to make the space for the cement, all round the spigot, from 1 to 1½ inch; that width is required, in order that the cement may be firmly driven into the joint. When the space is very narrow, this cannot be done. On the other hand, when too wide, there is a waste of cement, and a risk of injury from unequal expansion. FIG. 3. Exhibits a profile view of these kinds of pipes when joined together. The spigot and faucet pipes are liable to burst from the great expansion of the spigot, and the risk of this accident is increased by increasing the space between the spigot and faucet, which requires to be filled with cement. FIG. 4. Represents a longitudinal section of two flanch pipes, and the modes of connecting them. A and B, show the parts of the pipes; and C and D, the flanches. These pipes are also joined together, and rendered air-tight, by interposing between the flanches rope-yarn, hemp, or some other pliable material, and iron cement, and then screwing up the faces of them by means of the bolts and screw nuts. FIG. 5. Profile view of the same kind of pipes connected together, A and B, the pipes; C and D, the flanches; E and F, the bolts. FIG. 6. Represents the method of joining spigot and faucet pipes when they are to have a turn or angle. This method is convenient when the place where the turn required to be made is previously known, and the pipes cast accordingly. FIG. 7. Exhibits the method of connecting spigot and faucet pipes when they have a round turn. A and B, the junctures of the pipes. FIG. 8. Represents a longitudinal section of the mode of joining pipes by means of what is called a _thimble joint_. The junctures of the pipes to be connected, are made air tight, as mentioned already, by iron cement. A, the thimble or small cylinder, with projecting edges, which unites the pipes B, C.