Though M. Senefelder had advanced thus far, he had not yet made application of the chemical properties of ink and water, which constitute the distinguishing characteristics of Lithography. That was reserved for a further discovery, also brought about by accident. The difficulty he experienced in writing words on the stone in the reverse way, induced him to adopt the plan of writing the letters on paper with a soft black-lead pencil, and then transferring them on to the stone by pressure. He subsequently used lithographic ink for the purpose; and in the course of his experiments he observed, that when a paper written on with lithographic ink, and well dried, was dipped into water on which some oil was floating, the oil adhered to the writing, and left the rest of the paper clean, and that this effect was most striking when the water contained some gum in solution. This discovery induced him to try the effect on printed paper; and, taking a printed page from an old book, he moistened it with gum-water, and afterwards sponged the whole surface with oil colour. The colour adhered to the letters, and left the paper clean, and after further experiments he succeeded in printing as many as fifty copies from a page of printed paper; the letters, of course, being reversed. The idea then suggested itself of transferring, on to stone, letters written with lithographic ink upon paper. The plan succeeded, and the principle of the art of Lithography was thus applied to practice. M. Senefelder, in his subsequent improvements, gave a slight relief to the letters by the original plan of using diluted aqua-fortis, by which means the impressions obtained were blacker. He also contrived the means of printing in colours from stone, by reversing the process of ordinary lithographic printing. To produce coloured prints, he left uncovered all the parts that were to receive the colour, and the other parts of the stone were covered with an oleaginous fluid, that quickly dried. On applying any water-colour to the stone, it adhered to the uncovered surface, and not to the covered parts, and that colour was transferred to paper by pressure. In this manner, by using several stones properly prepared, the different colours required were printed, and the effect of a coloured drawing was produced. Thus we perceive, that almost at the first invention of the art of Lithography, the ingenious inventor showed the way of applying it to the production of coloured prints, a process which has lately been carried to great perfection. Senefelder lived to see his invention extensively adopted, and to reap benefit from his ingenuity. He died at Munich, in 1834, after having been many years the director of the Government lithographic office; and, in the latter years of his life he received a handsome pension from the King of Bavaria.