The cause of both phenomena is that in the first case the fats that lie deep gradually work upward into the partly prepared surface and practically reëstablish their interrupted communication with the printing-color. In the second case, the small quantity of fat that has adhered merely to the surface has penetrated into the stone, so that it loses its effectiveness. Added to this, in the latter case, is the fact that the linseed oil, and the varnish prepared from it, acquire the property of losing their fats when they are dried in the air, and thus will take color poorly or not at all. This observation led to the invention of an artificial stone or stone-paper. (7) In contrast with preparation by wet wiping there is the wiping with dry and fatty bodies, which produces full acceptance of color on the partially prepared plate, while in the case of the fully prepared plate there occurs at least partial color acceptance or semi-preparation. As every property of the stone can be used for good impressions just as well as it serves in unskilled hands to ruin a design, so in this case; the lost parts can be restored through proper use of rubbing with a dry, fatty substance, and the clean, prepared portions of the plate can be smutted. There will be more about this. V SHORT REVIEW OF THE PRECEDING As the entire art of stone-printing depends on proper preparation, it will not be out of place to express my views as to the nature of the process. This will serve also as recapitulation. (1) Limestone has countless little pores. These can soak up fatty as well as watery substances. (2) These can adhere easily to the limestone particles, but are easily separated again, as long as the nature of the stone is not altered. This alteration is produced most readily by sulphuric acid, tartaric acid and phosphoric acid. (3) Water evaporates from the pores as the stone dries. Gum and other slimy substances do not. (4) Fats soak into the stone more and more. There is no means of destroying them except to remove the limestone itself by grinding or etching. (5) Printing-color cannot adhere to the stone so long as a proper amount of moisture forms a wall between it and the stone. Under any circumstances it adheres only poorly to the lime particles, and assumes great power of adherence only when the pores of the stone are filled with fat, which are pinched in them, so to speak, and with which the printing-color strives to unite because of mutual affinity. (6) This stronger adherence (or complete color reception) thus happens only when the outer color can reach and touch the inner fat. If the latter is deep in the stone, so that the communication is broken, it becomes difficult and the communication must be restored. (7) This interruption occurs either if the color is rubbed away by force and with help of moisture, or if a substance that closes the pores unites with the stone.