An ordinary thin-paper copying book may be used, and the copying done by transferrence. It is only necessary to place the page of writing in the letter book, just as one would use a leaf of blotting paper. The superfluous ink that would go into the blotting paper goes on to the leaf of the letter book, and showing through the thin paper gives on the -other side of the leaf a perfect transcript of the letter. Any excess of ink on the page, either of the letter or of the copying paper, is removed by placing a sheet of blotting paper between them, and running one's hand firmly over the whole in the ordinary manner. This ready transcription is accomplished by using ink which dries slowly. Obviously the ink must dry sufficiently slowly for the characters at the top of a page of writing to remain wet when the last line is being written, while it must dry sufficiently to preclude any chance of the copied page being smeared while subsequent pages are being covered. The drying must also be sufficiently rapid to prevent the characters "setting off," as printers term it, from one page on to another after folding. The formula for the requisite ink is very simple:

Reduce by evaporation 10 volumes of any good ink to 6, then add 4 volumes of glycerine. Or manufacture some ink of nearly double strength, and add to any quantity of it nearly an equal volume of glycerine.

Gold Ink

Mosaic gold, 2 parts; gum arabic, 1 part; rubbed up to a proper condition.

Green Ink

A good, bright green, aniline ink may be made as follows:

Aniline green (soluble) ............. 2 parts

Glycerine.......... 16 parts

Alcohol............ 112 parts

Mucilage of gum arabic .............. 4 parts

Dissolve the aniline in the alcohol, and add the other ingredients. Most of the gum arabic precipitates, but according to the author of the formula (Nelson) it has the effect of rendering the ink slow-flowing enough to write with. Filter.