Among the bodies available for chemical printing, limestone maintains an eminent place. Not only has it an especial property of uniting with fats,--sucking them in and holding them,--but it has, also, the same propensity for taking all fluids that repel fats. Indeed, its surface unites so thoroughly with many of the latter that it forms a chemical union with them, becoming practically impenetrable for oil colors and remaining constant thereafter in repelling them so that they cannot adhere perfectly. Therefore when a plate thus prepared is dry and covered entirely with oil color, it still remains an easy matter to wash it completely, using merely water for the purpose. This good property, combined with the low cost and the ease of obtaining the stone in Bavaria; then the advantage that it is easily polished and prepared; the further advantage that a stone of medium thickness can be ground as often as a hundred times and utilized for new work--all these properties combined made me willing to overlook a few faults, such as their weight, great volume, frequent unevenness of quality, and lastly the occasional danger of cracking. Thus I came to use these stones as the principal means for making my countless experiments, whose happy result has been to elevate stone-printing to an art by itself. Having stated the process and the character of this form of printing, it remains only to say a few words about its value. With every new invention there arises the question if it is useful, and if so, in how far, for science, arts, and industry. Therefore all who have no sufficient knowledge of lithography, will ask justly: What is its value? What advantages does it give that are not to be found in any other forms of printing? To answer this, let me say the following merely in advance till later descriptions of the various processes will convince in themselves. It is the nature of earthly being and of human imperfection that rarely is anything found that combines in itself everything to be wished for and required. So it may be said of stone-printing that it makes neither book-printing nor copper-plate printing entirely superfluous. It is possible that in the future, by perfecting the presses, lithography may equal book-printing in point of speed, as it does not now; but the convenience of the latter, enabling the printer, by merely setting cast characters side by side, to do with speed, accuracy, and symmetry what the writer can hardly do with all his skill and industry, gives book-printing its own eminent value. When, however, we come to many things produced hitherto by book-printing, such as statistical tables, letters, circulars, letters of exchange, bills of lading, visiting-cards and addresses, and other similar work, we find that these can be produced more conveniently, more readily, more cheaply, and faster and handsomer with lithography.