There are few photographers who appear to be aware of the many
beautiful phenomena of nature that can be studied by the aid of
photography. Under the title of "Schnee Crystalle," Dr. G. Hellmann
has published[5] a book on this subject profusely illustrated with
engravings and photo-micrographic collotypes from direct photographs
by Dr. R. Neuhaus.
[5] Rudolph Muckenberger, Berlin.
[Illustration: FIG. 62.--SNOW CRYSTALS. PHOTO BY DR. NEUHAUS.]
Dr. Neuhaus describes his method of photographing snowflakes in Dr.
Eder's Jarbuch, from which article we extract the most important and
interesting paragraphs: Were we to attempt to photograph snow crystals
in a perfectly cold room, the temperature is still higher than that
out of doors; moisture at once precipitates upon the carrier of the
object; the crystals would melt and evaporate after a short time. The
work must be done in the open, and perfect success can be expected
only when the temperature is near zero.
[Illustration: FIG. 63.--SNOW CRYSTALS. PHOTO BY DR. NEUHAUS.]
Snow crystals evaporate rapidly even in low temperature, and the work
requires to be done rapidly and with caution. Freshly fallen snow only
will give a good photograph, and as we are compelled to work in the
midst of the snow storm, the task becomes still more complicated and
difficult. Snow crystals but a short time after falling break, the
broken pieces freeze together and crystallization is destroyed. For
the illumination of snow crystals, transmitted light only can be used;
reflected light destroys the shadows, and injures the high lights,
and the result is necessarily but a very imperfect picture of the
object.
[Illustration: Photo by Martin. FIG. 64.--A NATURAL PHENOMENON IN
ICE.]
Diffused light, especially that of a dark winter's day, and during a
snow storm, is not fit for this kind of photo-micrographic work, and
we must resort to artificial light, preferably to that of a petroleum
lamp. To prevent heat action emanating from the illuminating ray cone,
an absorptive cell of alum solution should be interposed. As alum
solution freezes at about 20 deg. Fahr., chloride of sodium is added.
With Hartnark's projection system, at 31 mm. focus distance, from 5 to
7 seconds upon an erythrosine plate is ample.
[Illustration: FIG. 65.--PHOTOGRAPH OF FROST CRYSTALS. BY JAS.
LEADBEATER.]
Dr. Neuhaus has made photographs of more than 60 different ice and
snow specimens. The pictures of ice crystals much resemble those of
hoar frost, deposited after a cold winter's night. Of snow crystals,
the doublets are highly interesting, two crystals merged into one, and
those having passed through a moist stratum of air, when microscopic
drops of water will freeze into the hexagonal form, giving the picture
an appearance very much resembling cauliflower.
[Illustration: FIG. 66.--PHOTOGRAPH OF FROST. BY JAS. LEADBEATER.]
The most difficult question of all remains, the cause of the various
forms of the hexagonal crystals, which frequently change in the same
snowfall. Instead of advancing a new hypothesis, says Hellmann, it is
better to acknowledge that we know nothing positively in regard to
this. In our knowledge of the form and structure of the snow we have
made great advance since the time of Kepler, but after nearly four
hundred years, we cannot give a satisfactory answer to his question,
"_Cur autem sexangula? Why six-sided?_"
We do not know the special conditions which determine the formation of
one or the other form of snow crystals. We have found that a low
temperature favors the formation of tabular crystals; a higher
temperature the star shaped crystals; these groups show such
multifarious forms that it is necessary to seek for other causes which
influence the formation of snow figures. There is offered here a broad
field for new investigation and study.
We give a reproduction (Fig. 64) of a photograph of a curious group of
crystals. Some water had been left in a 10x8 dish on a winter day, and
a film of ice was seen floating on the surface. The formation of the
crystals and the floral design were so beautiful that it was taken out
and photographed. The delicate lace-like edging of the glacial tracery
is the result of the deposition of hoar frost while draining off the
water from the ice leaves and flowers and fixing the image in the
camera.
Quite recently Mr. Jas. Leadbeater has favored us with some account of
his beautiful work in this fascinating branch of photography, some
samples of which are here given. He first makes his windows perfectly
clear and waits for a keen frost. The camera is inside the room and a
dark cloth-covered board is placed on the outside, leaning against a
low balcony of wood. The exposure varies with the thickness of the
crystals, from two to ten seconds, principally with a very small stop.
Two reproductions of his pictures will be found on pp. 76-77.