The following is a process to which all cast-iron water pipes should be submitted. It was introduced by Dr. Smith, and is equally applicable to any other casting that can be manipulated:--Each casting is thoroughly dressed, and made clean and free from the earth and sand which cling to the iron in the moulds, hard brushes being used in finishing the process to remove the loose dust. Every casting must be likewise free from rust when the paint is applied. If the casting cannot promptly be dipped after being cleansed, the surface must be oiled with linseed oil to preserve it until it is ready to be dipped. No casting is on any account to be dipped after rust has set in. The coal-tar pitch used as a paint in this process is made from coal-tar distilled until the naphtha is entirely removed and the material is deodorised. In England it is distilled until the pitch is about the consistence of wax. The mixture of 5 or 6 per cent. of linseed oil is recommended by Dr. Smith. Pitch which becomes hard and brittle when cold will not answer for this use. Pitch of the proper quality having been obtained, it must be carefully heated in a suitable vessel to a temperature of 300° F., and must be maintained at not less than this temperature during the time of dipping. The material will thicken, and deteriorate after a number of pieces have been dipped; fresh pitch must, therefore, frequently be added, and occasionally the vessel must be entirely emptied of its old contents and refilled with fresh pitch. The refuse will be hard and brittle like common pitch, and consequently worthless for the purpose. Every casting must attain a temperature of 300° F., either by previous heating or during the immersion before being removed from the vessel of hot pitch. It may then be slowly removed, and laid upon skids to drip. In the case of water pipes, all those of 20 inches diameter and upwards will have to remain at least 30 minutes in the hot fluid to attain this temperature. The coating when cold should be tough and tenacious, and not brittle nor have the slightest tendency to scale off.