270. The instructions given on printing, thus far, are by no means to be considered exhaustive. An effort has been made to inform you only as to the best known methods for producing ordinary photographic pic-tures, and to try to induce you to excercise care, cleanliness, taste, neatness, and economy in produoing them. Should you desire to go farther, Mr.Charles W.Hearn, in his admirable work, the Practical Printer, which should be in the hands of every printer, will lead you into all the realms of "fancy," "glace," and "porecelain" printing, and give far more elaborate instructions throughout than it is the province of this rudimentary work to undertake.

271. Printing surfaces, too, are as various as the processes. Photographic prints can be made upon almost any substance sufficiently plane to enable one to secure contact with a negativ,and non - absorhent, and smooth enough to receive the proper materials for printing thereon. Prints are made upon fabrics of all kinds, metals, mica, wood, porcelain, stone, leather, the human skin, enamel, animal pelts, and what not, from negatives, and by many other methods on various substances.

272. But printing is not confined to the use of salts of silver, as, besides the aniline,the platinum,and the carbon processes well known for years there are various so-called photo-mechanical methods of printing photographic pictures. The moat ingenious of these bears the name of its inventor, Mr. Walter B. Woodbury. Almost all the others - are founded upon one principle. With them the means of producing the printing surfaces are varied, but the printing proper is much the same as lithographic printing, and Is done in the same sort of a press. None of them displace silver printing for every - day photographic custom-work, and so they will not be treated of further hen-, hut will he given more attention in a lesson further on, with some hints as to the manner of working them.