There is little to be added to the description of the process of Lithography, beyond that given by the original inventor in 1819, the principal advances that have been made in the art having consisted in improved methods of manipulating. The ink now generally employed for drawing on the stone consists of equal parts of tallow, wax, shell-lack, and soap, mixed with about one-twentieth part of lamp-black; but the composition is varied, according to the kind of design to be executed. For writing or drawing upon paper, to be transferred to the stone, more wax is added to the ink, to give it greater tenacity. The drawing upon paper, to be transferred to stone, is not attended with any difficulty, and may be done by ordinary artists. The ink is applied with a pen, or camel's hair pencil, and when the effect of chalk drawings is required to be imitated, the ink is shaded by means of stumps, similar to those used in chalk drawings on paper. Some artists prefer to work directly on the stone with a camel's hair pencil, or with a composition called lithographic chalk. To transfer the drawing from paper on to the stone, the paper is first sponged with diluted nitric acid, which decomposes the size, and renders it bibulous. After being placed for an instant between blotting paper, to remove superfluous moisture, it is laid with the drawing downwards on the stone, which is slightly warmed. The stone is then passed through the press, and the drawing adheres firmly to it. To remove the paper, it is wetted at the back with water, and, when quite soft, it is rubbed with the hand. In this manner every particle of the fibrous pulp is cleared away, and the drawing or writing in ink remains as if it had been drawn directly on the stone. To prepare the stone for taking the ink, gum water is poured upon it, and it is rubbed over with a rag containing printer's ink, which serves to blacken the writing and prepares the lines for afterwards receiving the ink. The lithograph thus prepared is given to the printer, who first etches it, in the manner originally practised by M. Senefelder. The nitric acid employed for the purpose is diluted with about thirty parts of water, and it is poured over the stone whilst it is inclined on one side. This process is repeated several times, the object of it being not so much to give relief to the lines, as to roughen the surface of the stone, and thus facilitate its absorption of water. The nitric acid also removes the alkali from the drawing ink. In printing, gum is added to the water with which the stone is moistened, as an additional preventive of the ink adhering to those parts not drawn upon. The printing ink is applied with large rollers, and the damped paper having been placed carefully upon the stone, with blankets at the back, it is passed through the press.