The process of manufacture as it is carried on at Niagara is interesting. The visitor is first taken into the rooms where are stored the crude material, the sand, coke, sawdust and salt. The sand is of the finest quality and very white. The coke is first crushed and screened, the part which is reduced to sufficient fineness is mixed by machinery with the right proportion of sand, salt and sawdust. The coarser pieces of coke are used for what is called the core of the furnace, which will be described later on. This mixture is carried to the furnace-room, which has a capacity for ten furnaces, but not all of these will be found in operation at one time. Here the workmen will be taking the manufactured material from a furnace that has been completed, and there another furnace is in process of construction, while a third is under full heat, so that one sees the whole process at a glance. These furnaces are built of brick, about sixteen feet in length and about five feet in width and depth. The ends and bed of the furnace are built of brick, and might be called stationary structures. The sides are also built of brick laid up loosely without mortar; each time the material is placed in the furnace, and each time the furnace is emptied, the side-walls are taken down. A furnace is made ready for firing by placing a mass of the mixture on the bottom, and building the sides up about four feet high (or half the height when it shall be completed). A trough, about twenty or twenty-one inches wide and half as deep, is scooped out the whole length of the pulverized stuff, and in this is placed what has before been referred to as the core of the furnace, namely, pure coke broken into small pieces, but not pulverized, as in the case of the other mixture. The amount used is carefully weighed, so as to have the core the proper size that experiment has proved to give the best results. The core is filled in and rounded over till it is in circular form, being about twenty-one inches in diameter. At each end of the furnace the core connects with a number of carbon rods--about sixty in all--that are thirty inches long and three inches in diameter. These carbon rods are connected with a solid iron frame that stands flush with the outer end of the furnace. On the inside the spaces between the rods are packed full of graphite, which is simply carbon or coke with all the impurities driven out, so as to make good electrical connections with the core. This core corresponds, electrically speaking, to the filament in an ordinary incandescent lamp, only it is fourteen feet long and twenty-one inches in diameter. The mixed material is now piled up over this core, and the walls at the sides are built up until the whole structure stands about eight feet from the floor--a mass of the fine pulverized mixture, with a core of broken coke electrically connected at the ends. It is now ready for the application of electricity, which completes the work.