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 printing process, several of which are described herein, by which we may produce permanent photographic prints.

Many, however, are debarred from its practice by the want of a proper practical manual of instruction.

The object of this work is to observe, collate, and condense, as far as possible, the best and most practical thoughts of the few who have experimented with, and written on this process, not only abroad but at home, and to combine them with my own experience and observation.

I am particularly indebted to my friend G. Wharton Simpson, A.M., editor of the “Photographic News,” London, whose excellent manual “On the Production of Photographs in Pigments — Swan's Process” — has recently been given to the world, and who is one of the earliest experimenters in the process. I also gratefully acknowledge the receipt of some useful and practical ideas from Dr. Herman Vogel, editor of the ''Photo. Mittheilungen'', Berlin, translator and author of a revise of Mr. Simpson's work.

By careful and extended experiment I am able to indorse their views, and to add a few notes here and there of what has occurred to me in my own practice, and several other matters which I trust will be found useful. It is more difficult to sift out from a large amount of thought and record that which is most important to know—using one's brains as a sieve or filter to separate the good grain from the tares—the sediment from the