ll temperatures
will lead to confusion, and nothing will be learned. Some negatives
require a special treatment, and both printing and development must be
altered, while for a very dense negative the paper may be left out in
a dampish room for some time. It will then print with less contrast
and more half tone. A thin negative is better printed by the cold bath
process, but negatives should be good and brilliant for platinotype
printing. Any one taking up platinotype and getting only weak prints
would do well to look to his negatives instead of blaming the paper,
as the high lights should be fairly dense, and the deep shadows nearly
clear glass.

Time for complete development should always be allowed; with a hot
bath fifteen seconds will be sufficient, but if a cooler development
is used, or the prints are solarized in the shadows, more time should
be allowed. When the deep shadows are solarized, or appear lighter
than surrounding parts, a hot and prolonged development is required to
obtain sufficient blackness, as they have a tendency to look like
brown paper. I have found breathing on solarized shadows useful, as in
the presence of slight moisture they begin to print out and become
dark before development, getting black almost directly the print is
floated on the oxalate. Three or four acid baths of about ten minutes
each are used, and the prints are washed as before. The process
throughout takes much less time than silver printing, and can be kept
on all the winter, when it is nearly impossible to print in silver.
Prints can be developed in weak daylight or gaslight, and prolonged
washing is dispensed with.--_N.P. Fox, reported in Br. Jour. of
Photo._

* * * * *

[Continued from Supplement, No. 706, page 11283.]

ON ALLOTROPIC FORMS OF SILVER.

By M. CAREY LEA.

In the first part of this paper were described certain forms of
silver; among them a lilac blue substance, very soluble in water, with
a deep red color. After undergoing purification, it was shown to be
nearly pure silver. During the purification by washing it seemed to
change somewhat, and, consequently, some uncertainty existed as to
whether or not the purified substance was essentially the same as the
first product; it seemed possible that the extreme solubility of the
product in its first condition might be due to a combination in some
way with citric acid, the acid separating during the washing. Many
attemp