The Sun.
London, England, 1860-07-23 00:00:00

VARIATION OF LIGHT DURING TEE
ECLIPSE.

TO THE EDITOR OF THE SUN.
SIR,—For the purpose of examining some of the
results of the eclipse more carefully I went this day
to Carshalton, to study the effects of the veiling of
the sun upon the landscape, and to measure by my
photometer the diminution, of light, in the same
manner as I did at Blisworth, at the last great

eclipse of the sun.
The day for the country was lovely in the ex-
treme, light clouds broke the monotony of the sky,
and the first and last contact and contact with the
spots on the sun were most distinctly seen.
I made three sets of observations with the pho-
tometer, one upon the clear sky, as near the zenith
as passing clouds would permit; a second upon a
.spot a little above the horizon to the north; and a
third upon the illumination of the earth's surface.
The most interesting feature connected with the
veiling of so large a portion of the sun's disc was
the apparent limitation of diffused light. This
characteristic began to be decidedly apparent about
25 minutes after the first contact, and the appear-
ance of the landscape was greatly altered. The
noble trees in Beddiogton Park and the adjoining
domains were thrown into outline, and the effect of
perspective was diminished. Trees in outline at a
distance from buildings apparently touched them,
or were placed iq apparent contact with other trees
a long distance off.
This phenomenon was remarked by all the ob-
servers present, and gradually increased to the
period of greatest obscuration, when all the trees ap-
peared to touch each other, and the under branches
lost their green colour and became black. At half-
past three perspective was again resumed, the trees
and buildings apparently regained their normal
positions and assumed their usual appearance.
During the obscuration a paper mill which had
been recently painted white assumed a dull gray
colour. The bright yellow green of the walnut
was altered in colour, and there was an absence of
that bright reflected light from every object which
it was so peculiarly the province of the genius of
Turner to depict.
I was most anxious for a cloudless sky to obtain
the law of the diminution of light in the sky by an
extensive series of observations during an eclipse,
bait this day fate ordained otherwise, and clouds
and mist interrupted the series, which nevertheless
was fraught with interest. The light of the sky
near the zenith dropped from 11 to 7.25, when it
rose gradually to 10, at the termination of the ob-
servation. As a consequence of this, diffused light
was materially lessened, which contributed to the
curious phenomena detailed above.
During a great portion of the time the sky was
clear over the S.E. horizon, and I found that the
light at 3.5, a little after the greatest obscuration
had dropped from 11 to 7.50.
Upon comparing the amount of illumination with
observations made last summer in Switzerland, I
found that the light of the sky yesterday, about
the time of greatest obscuration, was 1 75 less than
we found it at the grand plateau of snow before the
last ascent is made of the Cima de Jazi, at an alti-
tude of about 12,800 feet, a situation where, after
the biting cold of the summit, observations could
be made with comfort and ease.
From measurements made in the north, a few
degrees above the horizon, where a dark elm cut
the sky, which was in that quarter clouded during
the whole period of the eclipse, the light dropped
from 11 to 8 ; but, although this diminution was
interesting and. confirmatory, the clouds spoiled the
observations of the particular knowledge of the
light of the sky, which I desired so much to obtain.
The intensity of the illumination of grass and
dark objects close at hand diminished exactly in the
same ratio as the light of the sky, and diminished
11 to 7.25, and the light upon a white painted
greenhouse varied in like manner.
During the whole of the eclipse a chorus of
thrushes were heard at intervals in every direction.
Between 2.40 and 2.50 I did not hear one, which
might have been an accidental circumstance, as
sparrows chirped, martins flew about, swans sailed
as usual up the stream. Trout were not deceived
by the darkness to come up as they are wont for
their evening gambols, and as far as I can judge,
the animal creation were not in any way affected.
At 2.10 a dark cloud arose in the S.W., the wind
freshened and whistled through the trees, and a
sensible chillness was felt. This cloud passed away
in about 20 minutes, and left the eclipse visible,
with but trifling interruptions, till its termination.
Until this day my mind has never realised to it-
self the importance of the sun's disc, but it is now
clear that if the rays of the sun emanated from a
point instead of a surface, the landscape would be
shdrn of a great part of its beauty, and would look
much as it does when lit up by the electric light,
when outlines and black shadows are the leading
characteristics. I have never been more delighted
than I have been this day in watching the return of
the natural appearance of the country after it had
been so completely altered, and the image of the
wonderful change effected by the veiling of the
sun's disc will always remain impressed upon my
mind with a sense of the great beauty which is at-
ributable to the universal diffusion of light.
I am, sir, your obedient servant,
ALFRED SMEE.

7, Finsbury-circus, July 18.

TO THE EDITOR OF THE SUN.
Sir,—l attentively noticed the eclipse of Wednes-
day on Primrose-hill, and my observations differed
in some respects so materially from Mr. Hind's,
made in Regent's-park, that, although merely taken
for my own information, they may not be unworthy
a place in your columns.
To determine the temperature with accuracy I
had two thermometers of the ordinary kind, made
by two different makers, the only appreciable dif-
ference between them being that one was a little
more sensitive than the other, falling and rising
with more rapidity.

Thermometer in the shade
2 ft. from the ground.
21 min. after the eclipse commenced, Greenwich
time being 20 min. to 2 67 deg.
Gradually fell until 11 min. to 3, the period of
greatest obscuration
At 3 o'clock
Both thermometers marked this, and there was
no perceptible variation until 25 min. past 3,
when a rise commenced, and at 4 o'clock, 6
min. after the end of the eclipse

At 5 o'clock
At 6 o'cldck
At 8 o'clock

6 „
58 ~

These results do not much differ from those given
by Mr. Symons. But Mr. Hind gives the thermo-
meter at 20 min. to 2, 70 deg.; half-past 2, 69 deg.;
at 4 o'clock, 68 8 deg. Yet Mr. Hind himself felt
the change in the temperature, although' is ther-
mometer failed to register it ; for at 2h. 32min. he
records " sensibly cooler."
I am an observer of light, and am conversant
with the changes in the landscape created by varia-
tions of light and of clouds and of mist. I think
few better places than Primrose-hill could be found
near London for seeing the effect of light during an
eclipse, and I agree generally with the observa-
tions made by Mr. Hind. At the period of the
greatest obscuration a mistiness had arisen; the dis-
tant parts of the landscape were hidden ; Highgate
seemed enveloped as if a heavy blight hadisettled
there; and, although not certain, yet my belief is
Highgate church was obscured. For just at this
time, the middle of the eclipse, the sun shone
clearly—there was a pale yellow light thrown over
the tops of the houses in W.S.W. that was beauti-
ful, but indescribable; and, although different, yet
it somewhat resembled a brilliant moonlight effect
on a clear August evening, and the study of this
extraordinary effect occupied most of my attention.
I therefore disagree from Mr. Symons, and think
the effect upon the landscape different from and far
beyond any mere diminution of light, and that the
action of the sun's rays so greatly lessened, with
the sun so high in the heavens, was wonderful to
behold.—l am, sir, your obedient servant,

WILLIAM RAY SMEE.
St: Edmund's-terrace, Regent's-park, July 20.

TO THE EDITOR OF THE SUN. 1
SIR,—I am induced to forward you the accom-
panying
details of the eclipse as seen from this
observatory, inasmuch as they possess some interest
in connection with those of Mr. Hind, published in
your impression of Thursday. The first contact of
th© moon's limb with the sun took place at lh.
40m. 455. local men time. The advancing limb of
our satellite was exceedingly rugged, four high
mountains being very conspicuous as she came on
to the solar disc. It is a curious fact that the moon
appeared to have the effect of stilling the undula-
tions of the solar limb at the points at which she
cut it. Mr. Hind's large dark spot was centrally
bisected at lh. 57m., and soon afterwards the ad-
vance: of the moon disclosed a regular sierra of
mountains to the south of those already seen. At
2h. 37m, 40s. the moon's limb was centrally over
the westernmost of the two remaining large spots,
whence it steadily advanced, and covered the east
spot centrally at 2h. 46m. 2s. For some time after
this the effect of the sunlight as seen with the naked
eye was remarkable; a dimness and dulness of a lurid
tint seemed to overspread the landscape. Some-
thing of the sort might have been produced by a dense
veil of mist covering the sun ; but the continuance
of sunshine, and the sharpness of theshadows thrown
by posts, rails, and trees, at once must have shown,
even to a person ignorant of the eclipse, that this
curious diminution of light had no reference to any
merely atmospheric cause. The effect of comparative
darkness was very considerably' more striking than
on the occasion of the larger eclipse of March 15,
1858,
as on that day the dense impenetrable nimbi
only conspired with the obscured sun to give.the