The Indianapolis journal. [volume] (Indianapolis [Ind.]) 1867-1904, 1883-04-21
SPOTS ON THE sun.

Written for the Journal by William Dawson, Spice
land
Many persons have heard OF spots on the
sun, though not so many, perhaps, have
learned that the sun spots are very change
able in their formation and size There are
many more sometimes than at others-being
periodical in their appearance in greatest
numbers. The periods from one maximum
to another are generally Of about eleven
years duration. ] began a series of solar OBJ
seryations in March, 1867, which has been
continued to the present time. The telescope
used was an schromatic six feet long and
four and six-tenths inches aperture. A mag
nifying power of 100 has been generally used,
though in certain cases a power OF 200 was
applied, and in others only fifty. For many
days during the spring and summer of 1867
no spots were TO be seen. Toward winter
they began to appear so as 10 make observa-
ton of more interest, By spring, 1863 thirty
or more sun spots were sometimes
counted at one observation. A few
months later sixty or seventy were
occasionally seen. l had never heard or read
or more than about 200 being seen at one
time, and now began to feel interested to see
ii might be able to count as many sun-spots
as anybody else had seen. Observations were
continued, and spots on the sun were found
to increase in number, and they grew in size
also. But the increase is by no means regu-
lar and steady. 1t is rather by apparent
spurts or jumps. A sun-spot lasts only few
weeks, and sometimes but a few hours. For
instance: Oct % 1868, eleven spots were all
7 hnf I'M in ct a off r1 I cd
100. Nov. s, only one solar spot was to be
seen; fifty-four were visible on Jan. 28 1869;
none on April 7. e four days sixty had
come into view, 1870 on May TO- and only
twenty were seen ON May %. Two causes
operate in producing these apparently sudden
changes, viz: the suns rotation on its axis,
and the actual formation and vanishing of
spots One day the sun may look clear and
white; in a day or two, by turning on its
axis, a group of several dozen spots may come
into view. They first appear on the east side
or edge OF the sun, move westward as the sun
revolves, and in twelve or thirteen days
disappear behind the western edge
of the sun. We thus learn that
the sun makes a complete revolution on its
axis in about 25K days. Some spots form
and vanish in short time, and some OF the
larger ones continue month or two and re-
appear a second time. When many spots
occur they are nearly always located in
groups or clusters. Indeed, this is their gen
eral disposition.
But now imagine my delight when on June
3, l saw 225 spots on the sun. They were dis
posed in eight groups scattered over the
solar face. One group had 120 spots. In
making this observation 1 used a power of
200, which makes the sun look very large
on q scale which would more than fill the
sky from horizon to zenith. June IA, only
twenty-one spots were to be seen. But on
the oath more than 200 appeared again. They
-, H.
would seem to have been the climax for 1869.
In the following year the SUMS activity
was renewed with more than double its
wonted force. As the spring and summer
passed 300 to 400 spots were often visible.
And the great maximum occurred on
August 81 with a show of $50 sun spots,
nearly five times the highest number that l
have been able to find or hear of in previous
records $40 of these spots were grouped in
| two vast clusters and twelve more groups
dotted the central zone of the sun. would
| say here that ii any reader knows of more
| than 200 sun spots being seen at one time
| should be glad to have him communicate the
| fact 10 me. After this the spots decreased in
number-not regularly, nor even so rapidly
as they increased from 1867 to 1870, for the
minimum did not occur until March, 1879.
This period, then, from one minimum 10 the
next, was twelve years-one year longer than
the average length. Some periods are hardly
ten years. In the late maximum, about one
year ago, / only observed 175 spots on the
sun: seemingly about the usual number at
maximum, though a small show as compared
with the one twelve years before The
largest spots are fewer and of less size than
those of 1S70-73. l observed the sun TO be
entirely without spots on Feb. %. A noted
astronomer of England alludes to this as
matter of interest. being so soon after max
imum.
On the odd nit. l counted ninety-ive
Spots the greatest number for some time.
There is now nice show of sun spots in
reach of a moderate spy-glass. The size of
solar spots varies all the way from mere
dot as seen in the telescope to a large spot
having diameter of thirty-fve or forty
thousand miles. Indeed, some have been re-
ported larger than this. Such a one may be
seen with the naked eye protected by
shade CLASSY very easily. By careful looking
earth, say 5000 or 5000 miles across, without
the telescope. Bat a casual observer will
hardly find one less than about twice this
size without the aid of glass.
1t may be remarked that extensive out
bursts of solar spots are attended, or soon
followed, by great auroras and electrical dis
turbances The connection between these
three phenomena seem close and general.
Notable instances occurred April 16 and No.
were large enough to be seen with the naked
eye, and through telescopes the changes in
| form, etc. were found to be very active, in
dicating great cyclones on the sun. Many
| people witnessed the brilliant auroras on
| these occasions, and telegraph operators were
bothered in sending messages.
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Art in St. Louis.
Art School Letter in Courier Journal.