Evening star. [volume] (Washington, D.C.) 1854-1972, 1891-08-22
DO TORNADoEs WHIRLs
An Interesting Paper Read Before the Sec
ton of Physics This Morning.

DO TORNADOES WHIRL3
An Interesting Paper Read Before the Sec.
| ton Of Physics This Morning.
"Do Tornadoes Whirl?'' was the title of q
paper read by H. A. Hazen before the section
of physics today. The speaker first showed
that there was q well-nigh universal belief
among the people that there is always whirl
in tornado cloud, but that this was based
not SO much upon actual facts az
upon a general theory. This belief may be
hkened to the almost universal opinion
among the people that the moon has an effect
on the weather, which, however, it has been
proved is not the case by comparing observa-
tions Of the weather tor more than a century.
The speaker suggested two methods Of solving
| the problem, first, by actual observations of
| the funnel cloud as 1t passes any person, and,
| second, by studying the distribution Of the de-
| bris after the tornado has passed. One grea.
difficulty in observing the tornado is due to
terror induced in the person by its presence.
! another ia due to a great cloud of dust
| which hides the phenomenon. If the OBJ
| server is on the south side it is very
dlihcult to separate the appearance. due to the
forward movement of the funnel from that
due to the whirl. This difficulty, however.
vanishes on the north side, because here the
whirl would tend to carry the debris back in
| the direction from which the funnel had come
Since the whirl has a velocity twice as great as
| the forward velocity if an observer on the north
side sees leaves, branches, &c, carried to his
right hand 1t Is good evidence Of whirl. The
distance of the observer, however should not
be greater than 500 feet
The second method seems capable Of settling
this question better than the first because one
can study carefully the effects IT bis leisure
and with no disturbance Of mind. Careful in
designations at the weather bureau on these
lines has shown a most marked result. The va.
ports OF between 200 and 800 tornadoes have
been received during the past two years and
the evidence from these reports is overwhelm-
lngly In favor of the view that there 10 no
whirl
Special mention was made Of the Akron,
Ohlo tornado OF May 10, 1890. Prof. Egbert
wrote that he went out to investigate the tor
nado with his mind fully made up to find evil
none.
He also forwarded chart showing that the
distribution of the debris indicated no whirl
whatever. Mr.. Curtis, who investigated the
Whkesbarre, Pa, tornado of August -, 1890,
found exactly the same result 1t was also
shown that precisely the same effect had been
noticed in Europe, while it would be unsafe
to say that the evidence WAS sufficient.
COLOR PHOTOGRAPHY.
The paper entitled Color Photography by
Lippmanns Process" by Chas. B. Thwing Of
Evanston, ILL.,, was read after The STARS re-
port closed yesterday afternoon. The state
ment was made that in q communication to
the Academic DIES Sciences on the I'd OF Febru-
airy last, Mons. G. Lippmann opened an en-
tirely new line OF experimentation on the prob
lem OF the Photographic reproduction OF the
colors of nature. To Lippmann's account of his
discovery is appended in Complies Renus anoto
by Mons. Edw. Becquerel to the effect that the
process of Lippmann differs radically from the
discovery made by himself in lS4S. in that while
Ran nl,1
to produce a colored image of the spectrum.
which could not be exposed to light, since tho
action of the usual fixing agents reduced tho
deposit to mere film Of metallic silver, Lipp-
mann, on the other hand, had by physica.
process obtained an image which retains its
colQrs after treatment with hypo-
sulphite Of soda, and is, therefore,
as permanent an ordinary negative.
The peculiarities of Lippmann's method
consist, first. in the use of plate which is
transparent and free from grains; second. in
the exposure of the plate with its film side rest
ing against a rejecting surface Of mercury.
The interference Of the reflected with the incl
dent ray Of light divides the film into a num-
Der OF layers at the maxima, which will CORE
spond in their distance apart with the wave
length of the incident light, and will therefore
be able to reproduce by reflection the color
which produced the layer.
Lippmann says that the plates are positive
for reelected and negative for transmitted light
lneSatu par trausparence). by negative he
means showing the Complementary color. In
that one OF Lippmann's negatives which
have seen and all those obtained by myself, the
plates are opaque to transmitted light, showing
only differences of density like an ordinary
negative. The reverse side Of the plato, how
ever, shows the complementary colOrs some
what fainter than the original colors which ap-
pear On the film side Of the plate.
In my experiments | used both aibumen and
collodion films, securing transparency by re-
ducing the proportions OF the salts to about
one-fourtb the amount usually employed. The
plates were exposed against mercury, not. how
ever. to the spectrum, but to light transmitted
being to determine whether the ordinary colors
Of rays of several different wave lengths, would
be reproduced with the same fidelity as were
the pure rays Of the spectrum.
The results obtained. though by no means
conclusive at all points seem to indicate: First,
some fair degree of accuracy, notifications
being introduced by change Of thickness of
the film between exposure and final drying and
bya shortening Of the distance between maxi
ma, caused by the rays striking the reflector at
an angle other than the normal. Second,
that exposure sufficiently long to give q
clear image of the red is quite certain to oblit-
crate the blue by overexposure. Third that
an overexposure may completely reverse the
colors, causing the original colors to appear on
the reverse, and the complimentary on the
film side of the plate.
number Of negatives were exhibited Illus
trating the facts presented.