Select a good paper and float it for a minute on the surface of the following solution:

Uranium Nitrate.......... ...................................................25grs.

Distilled Water................................................................ 1 oz.

Curl the sheet of paper when floating, to expel the air and avoid air bubbles. This should be done by lamp light. The paper is now quickly dried in subdued lamp light or in the dark room and it is ready for printing. The coating is a weak brown in color and the printing will appear as a chocolate brown. After printing, the paper should be washed in running water but not in the stream. If it is now sponged with a solution of the result will be a deep violet print.

Chloride of Gold................... ...............................................2grs.

Distilled Water................................................................ 1 oz.

If, after printing and washing, it is put into a two per cent solution of red prussiate of potash a fine red print will be the result. If printed and washed and immersed for a minute in a five per cent solution of cobalt nitrate the result will be a green print and it should then be put in the following solution, washed and dried:

Distilled Water............................................................ 1 oz.

Sulphate of Iron....................................................20grs.

Sulphuric Acid....................................................... .....16 drops-

Of course in all instances the print must finally be washed thoroughly before drying.

There are numerous other simple papers which the amateur can prepare but we will not devote our attention to some of the staple goods on the market. Most of the papers just described come under the class of

"printing out papers," generally known as P. O. P.

Let us now consider some of the papers of the second class, or "developing papers."