"Mr. John Spiller communicated to the London Chemical News (1861) a paper on the employment of carbon as a means of permanent record. The imperishable nature of carbon, in its various forms of lamp-black, ivory-black, wood-charcoal, and graphite or black lead, holds out much greater promise of being usefully employed in the manufacture of a permanent writing material; since, for this substance, in its elementary condition and at ordinary temperatures, there exists no solvent nor chemical reagent capable of affecting its alteration. "The suggestion relative to the mode of applying carbon to these purposes, which it is intended more particularly now to enunciate, depends on the fact of the separation of carbon from organic compounds rich in that element, sugar, gum, etc., by the combined operation of heat and of chemical reagents, such as sulphuric and phosphoric acids, which exert a decomposing action in the same direction; and by such means to effect the deposition of the carbon within the pores of the paper by a process of development to be performed after the fluid writing ink has been to a certain extent absorbed into its substance--a system of formation by which a considerable amount of resistance, both to chemical and external influences, appears to be secured. An ink of the following composition has been made the subject of experiment: "Concentrated sulphuric acid, deeply colored with indigo .......... 1 fluid ounce. Water, .............................. 6 " " Loaf Sugar,.......................... 1 ounce, troy. Strong mucilage of gum-arabic 2 to 3 fluid ounces. "Writing traced with a quill or gold pen dipped in this ink dries to a pale blue color; but if now a heated iron be passed over its surface, or the page of manuscript be held near a fire, the writing will quickly assume a jet black appearance, resulting from the carbonization of the sugar by a warm acid, and will have become so firmly engrafted into the substance of the paper as to oppose considerable difficulty to its removal or erasure by a knife. On account of the depth to which the written characters usually penetrate, the sheets of paper selected for use should be of the thickest make, and good white cartridge paper, or that known as 'cream laid,' preferred to such as are colored blue with ultramarine; for, in the latter case, a bleached halo is frequently perceptible around the outlines of the letters, indicating the partial destruction of the coloring matter by the lateral action of the acid.