The study of crystallization is undoubtedly an interesting and
fascinating one, and photography may be made to play an important part
in securing permanent records of these curious formations. If a drop
of water containing a salt be allowed to drop upon a glass plate, it
will, upon evaporation, deposite crystals of various kinds. In a
recent article in _La Nature_, by Dr. E. Trouessart, a description is
given of the beautiful crystallic forms deposited by a drop of ink on
evaporation. The article is translated in the _Literary Digest_, from
which we make extracts:
"Take a sheet of glass, deposit on it a drop of ink and spread the
drop a little, uniformly; let it dry for a few minutes; then examine
with a microscope, magnifying from 50 to 200 diameters, and you will
be able to see the flowers of ink in process of formation under your
eyes; that is to say, regular white crystal particles which detach
themselves from the black or violet medium, and arrange themselves so
as to form regular figures.
"If you are pressed for time, this beautiful result will easily be
obtained by passing the sheet of glass over a spirit lamp or a candle
to evaporate the moisture. The crystals will then be smaller and more
numerous, presenting the appearance of a dark firmament densely
sprinkled with bright silvery stars. But if you have patience to wait
for evaporation without heat, you will obtain larger crystals of more
varied forms, arranging themselves as crosses, flowers, etc.
"These crystals may be varied indefinitely by modifying the
compositions of evaporation, adding more ink, etc. But it is quite
possible that different inks will give different results. The inks I
use, like all the other inks in use, have a basis of sulphate of iron
and gallic acid.
[Illustration: From "The Literary Digest." FIG. 67.--INK-CRYSTALS, AS
SEEN THROUGH A MICROSCOPE.]
"By allowing the evaporation to proceed slowly, it is quite easy to
watch the formation of the crystals. The geometrical figures are more
or less perfect cubes, pyramids, lozenges, crosses, needles, etc., the
pyramids being formed by cubes superposed one on the other, as in the
pyramids of Egypt. The _flowers_ in our illustration are formed by the
union of crystals, each of which represents the petals or sepals of a
flower. The Maltese cross--the crucifer or four-leafed flower--is the
normal regular form, but multiples of four frequently occur, by the
formation of new crystals in the intervals; and also by the accidents
of crystallization, we get flowers of three and five petals,
resembling _Rubiaceae_, lilies, orchids, violets, etc."