Thus far carbide has been found industrially valuable for two other purposes. The one is for carbonizing steel; experiments in Germany show that iron or soft steel takes up carbon more readily when it is heated with carbide than when it is heated with coal dust or charcoal. Some steel works are now using carbide for this purpose. The other use of carbide is more important. It is found to be a valuable germicide. It is said to be the most effectual preventive of black rot, and to destroy the _Phylloxera_, the two worst enemies of the grape. The action of the carbide as a germicide depends on its decomposition by the moisture of the soil, forming acetylene, which kills the _Phylloxera_. If the use of carbide on a large scale substantiates the claims made for it, this is a discovery of vast importance. The ravages caused by the _Phylloxera_ in the vineyards of southern Europe, of Africa, and Australia must be ranked as great national calamities. A temperature ranging from 2000° to 2500° C. (3600° to 4500° Fahrenheit) is required to make carbide. It is probable that this temperature can be economically attained only by the electric furnace using water power as the source of the electric current, and this is the only method used for making carbide, with the exception of the Walther process, which does not use electricity but depends on the intense heat generated by burning acetylene under pressure. In electric furnaces the formation of carbide depends simply on the heat of the arc, which fuses the mixture of lime and coke. The latest improvements on the first very simple forms of furnace have secured continuity of work and economy of electric energy. In the United States carbide is made exclusively in the Horry furnace. This furnace consists of a huge short cylinder or hollow wheel, mounted to revolve slowly on a horizontal shaft. The periphery of the cylinder is closed by removable cast-iron slats. As the cylinder is partly revolved on its axis from time to time, the slats are taken off from one side and replaced on the other, thus leaving the top always open. The cylinder is filled on one side with the powdered mixture of coke and lime. Into the mixture two vertical carbon electrodes project downward through the open top of the cylinder. As the carbide is formed, the cylinder is revolved, lowering the mass from the electrodes. The fused carbide cools, hardens, and is broken off and removed as it rises on the other side of the slowly revolving cylinder; new material is constantly fed in to maintain the level around the electrodes. The process in the Horry furnace is continuous; the furnace can be run without arresting the current until repairs are necessary. It is said to combine the different theoretical improvements referred to, and to reduce the cost of production. The Horry furnace is in use at Niagara Falls and at Sault Ste. Marie. At St. Catherine's, Canada, Willson is using his own furnace.