Evening star., 1949-03-07
Stors, Men and Atoms Il
Water Can Remain LIQUID
At-20 Degrees Centigrode
Experiments Conducted in Laboratory
Of General Electric Co.
Bv Thomas X. Henry

| ny HOWUS H. 41cUTV
Water doesn't always freeze at zero cent?
grade or 80 degrees Fahrenheit.
It may not start to become ice until the
temperature reaches as low as 20 cent?
grade, or almost so degrees Fahrenheit be-
low the commonly assumed freezing point.
The freezing point of water long has been
one Of the most fundamental constants in
physics-but actually it has no validity ac-
cording to experiments just reported to the
American Association for the Advancement
of Science here by DR.. Robert mith-Johann-
sen of the General Electric research labora.
tory.
Pure. motionless water remains water
down to temperatures seldom reached ex-
cept near the poles.
The point has been in controversy for some
time and is of considerable Importance in the
production of snow by seeding clouds in
which the pioneering work has been done by
the General Electric Co. Just after the war
the German physicist DR.. Wilhelm Rau
claimed to have carried pure water to q
temperature of 10 centigrade before ice
formation started but his measurements
since have been shown to be invalid.
Experiments Precise.
DR.. ith-Johannsens experiments were
carried out with the utmost precision and
the effect of various particles mixed in the
water on raising the freezing temperature
were determined. At temperatures above 30
centigrade. it was concluded there must
be some nucleus in water for the formation
OF ice crystals This might be dust par
ticle of any sort. or even a slight ripple.
Absolute purity and motionlessness. Of
course never would be achieved in nature.
Actually, the experimenter claims, water
never freezes at the hitherto commonly &C.
cepted temperature unless there is an ice
particle already present.
It was found that freezing took place in
two different ways at low temperature. Often
the water seemed to freeze with great rapid
ity from many locations to form an opaque,
milky ice easily recognized by the naked eye.
In some cases, however, single, beautifully
slowly out from widely separated nuclei.
Sometimes only one crystal developed In .
whole water sample.
#
The outstanding example of natural evolu-
ton at work in human experience is now
in progress-the creation of a race of black
butterflies
1t has been going on for the past century.
DR.. E. B. Ford, noted British geneticist has
reported to the international Genetics Con-
gress.
There has been a marked tendency for
butterflies and moths in industrial areas Of
the United States where there Is much
smoke in the atmosphere to grow darker
from generation to generation. This is by
no means case, 1t is explained, of in.
heritance Of an acquired character. the
possibility Of which is considered very doubt
full
The most likely explanation. Dr. Ford
said, is that there is a dark strain in many
species, the hereditary genes Of which are
tied up with greater hardness. This greater
natural resistance has enabled them to sur
vive better in a Smoke-filled atmosphere.
1t is case of the outcropping of a poten-
tiality present in the race all the time by
the stress of environment.
Appear in Other Areas
The dark species now are appearing In
areas where there Is no industrial develop
ment
This Is presumably the major way in
which new species and varieties of animals
have arisen in the world since the beginning,
1t is pointed out Ordinarily, however such
change takes place only over thousands
Of years SO that its progress is undesirable.
Here there Is a clear case of rapid evolution
through survival of the fittest. Blackness
apparently is quite incidental, Of no par
ticular advantage in itself.
Butterflies and moths tend to have cryptic
patterns on their wings as sort of camou-
fage to protect them from their natural
enemies. The blackening tends to destroy
this pattern. thus making the so-called
"melanistic" strains slightly less adaptable
in regions Of clear atmosphere. This may
be the reason why, in spite of their greater
hardness. they have not appeared before
1t is notable, the report points out, that
the blackening species all have the habit Of
resting in exposed positions where camou-
dage would be valuable
This is demonstration. it is explained. Of
the working of an almost pure Darwinian
doctrine.