In 1871, Silas P. Knight, of Harper & Bros., New York, invented the wet black-leading process, and in 1872 took out another patent for an improvement on this process. Mr. Knight's method of wet black-leading was not generally adopted by the electrotypers of that time and gradually became almost unknown. Undoubtedly, the cause of this was that the method of dry black-leading was good enough for type and woodcut work. The half-tone had not been invented at that time, and it was only after the invention of the half-tone that a better method of black-leading became necessary. Thirty-seven years after Mr. Knight had successfully used his process of wet black-leading a patent was granted to Frank L. Learman, of Buffalo, New York, for a wet black-leader. Since that time numerous patents have been taken out on different methods of using the wet process, which is universally recognized today as the best method of graphiting the surface of a mold. In 1870, Joseph A. Adams patented a process for covering the surface of the mold after it had been black-leaded with powdered tin. This was for the purpose of quickening the deposition of the copper shell when the molds were in the batteries, and from this undoubtedly came the oxidizing process of coating the surface of the molds with chemical copper invented by Silas Knight, which has long been and is now in use. Perhaps one of the greatest forward steps in the development of electrotyping was made when the plating dynamo was invented. The first adoption of a dynamo in place of Smee's battery took place in 1872. With the Smee type of battery it required from thirty to forty-eight hours to deposit a copper shell thick enough for commercial use. With the invention of the plating dynamo and its improvements, the time of depositing the shell was reduced so that now two hours is the common time that a mold is kept in the tubs or batteries. This quickening of the time required to deposit the shell was one of the most essential features in the development of commercial electrotyping. From the first hand-screw presses, which were successfully used for molding, to the modern high-power, motor-driven, hydraulic presses, for working either in wax or lead, is a far cry. The invention of the half-tone, together with the invention of the modern two-revolution cylinder press which has brought printing into its present state of perfection, made necessary radical improvements in the machinery for making electrotypes. These improvements have been steady in their development, but the fundamental points of the process are practically those which have been in use from the start of commercial electrotyping. ELECTROTYPING BY THE WAX MOLD PROCESS An electrotype is a facsimile printing plate duplicated from an original. The original may be either type, a woodcut, a zinc or a copper etching such as a line-cut or a half-tone, or it may be a combination of type-matter and line-cuts or half-tones.