er, wash the print in a few changes of water till the water ceases to
be tinged with the blue color of the print. If the fine details of the
picture wash out, the picture has not been printed long enough. If the
high or white lights in the picture are tinged with blue, then the
picture has been printed too long.

After the print is washed sufficiently, lay it between two clean pieces
of white blotting-paper to absorb the moisture, then pin it up by the
corner to dry.

It is very easy to sensitize the blue paper. Any unglazed paper will
answer, but the Rives paper is the best. The following formula was sent
a few days ago by Sir Knight Willis H. Kerr, University of Omaha,
Bellevue, Wisconsin:

No. 1.

Citrate of iron and ammonia 1 oz.
Water 4 "

No. 2.

Red prussiate of potash 1 "
Water 4 "

Keep the bottles in a dark place or wrapped in black paper. Mix equal
parts of No. 1 and No. 2, and having first dampened the paper with a
brush or sponge put on enough of the solution to tint the paper evenly
and apply lightly to avoid streaks. As soon as the paper is dry it is
ready for use. The operation of sensitizing the paper must be done by
gas or lamp light.

SIR KNIGHT FRANK S. WHITNEY asks how to mount prints made on Omega
paper without removing the gloss, and also wishes a good formula
for paste, and to know just how mounting of prints is done. Trim
the prints ready for mounting before they are toned. Tone them,
and squeegee them to the ferrotype plate. When they are thoroughly
dry apply paste to the back of the print before removing it from
the ferrotype. This will moisten the print just enough to let it
be removed from the plate without tearing or sticking, loosening
the corner first with the point of a pen-knife. Have the
card-mount ready, and lay the picture carefully on it just where
it is to be pasted. The prints treated in this way lose little of
the gloss made by the ferrotype plate. When first beginning to
mount pictures it is best to mark the place on the card where the
picture is to be pasted. Lay a piece of tissue-paper over the face
of the print, and rub the squeegee over it lightly. Take off the
paper, and if any paste has oozed out from the edges of the print,
wipe it off carefully. Then lay a fresh piece of paper over the
print