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PARHELIA; OR, MOCK SUNS.

Sq) BOUT a year ago the writer was walking
i} between New Brighton and Egremont, in
Cheshire, when his attention was arrested
by seeing in the clear blue sky a ball of
coloured light, globular in form, but with
curved projections from its upper and lower extremities:
it was of the apparent magnitude of the sun itself, which
was shining brightly at the time. This was about
11.30 a.m.

The distance of this mock sun from the real sun was
| about 25°. The ball of light appeared suspended in the
clear blue sky, from which it stood out in relief, though
its edges were not very definitely marked.

There was ‘scarcely a trace of cloud of any kind in the
sky at the time: none in the region of the parhelion.
This fact is important, as showing that an apparently
clear sky may contain vast aggregations of crystals. It
also gives evidence that the presence of those crystals
does not greatly affect the colour of the blue sky; for
there was nothing peculiar in the tint of the blue at this
time, nor did the tint alter with the phases and disap-
pearance of the phenomenon. These phases were as
follows :—

1. A single mock sun was seen west of the true sun.

2. An are of a supplementary halo, external to the
circle in which were the mock suns (for another soon
appeared) was seen near the zenith.

This halo was about 25° above the circle! in which the
pathelia were situated, and its convex side was towards
the earth.

3. Another ball of light, similar to the first, appeared
towards the east. It was not quite so brilliant as the
first, and also lay in the circumference of a halo of about
50°.

It is worthy of note that the are of the halo last men-
tioned did not appear at all below the parhelia: only its
upper portion was seen. (See Figure.)

1 This was only seen in part.

PARHELIA ; OR, MOCK SUNS.

That a stratification of vapour was taking place at the
time was manifest from a long wavy line that reached
out horizontally from the first mock sun for about 90°,
while across the dise of the ball there also appeared about
half a dozen thin curved lines, which had no apparent
continuance on either side.

The colours of the supplementary halo near the zenith
were reversed. The width of this halo was less than that
of the one below it; but its edges were more sharply
defined, and the colouring much brighter: indeed the
primary halo had little more than a reddish tint.

We must now notice the curved projections or tails
which proceeded from the mock suns. It will be seen by
the sketch that there were short horizontal tails as well
as the vertical ones already mentioned. One of these
horizontal ones coincided with the long wavy line men-
tioned above. This long line was probably due to linear
cirrhus; a form of cloud very often accompanied by pris-
matic phenomena, and indicative of weather change. In
the present case,a change from frost to thaw soon followed.

The colour of the upper and lower tails was red, as was
also that of the inner horizontal ones; while the outer
partook of the blue—thus corresponding with the colours
of the halo.

The phenomena was observed by me for about half an
hour.

Mr. Buchan, in his “ Handy Book of Meteorology,” gives
several figures to illustrate this part of the science: but
the present case is different from any of those which he
has brought forward, and it is difficult to assign any limit
to the varieties of form that may be seen; for the re-
fractive properties of crystals, &c., is dependent on
physical conditions which vary with temperature, &e.
The year just ended has been remarkable for the number
and severity of its thunderstorms, and has also been
marked by a great number and variety of curious optical
phenomena.

This is a subject worthy of further investigation.

The reader who desires to pursue this matter further,
will find assistance in Brewster’s “ Optics? ;” and singular
cases will be found recorded in the voyages of M‘Clintock
and other Arctic travellers, the ice crystals which per-
meate the air in high latitudes being favourable to their
production.

Imperfect parhelia or mock suns are not uncommon,
but a case similar to that described above is rarely seen.
In regard to their height, the writer had the opportunity
of observing, last spring, that they are occasionally caused
by the passage of loose cloud-drift probably at an altitude
of five or six miles. No doubt they are higher than this
at times.

In former days, when optics had scarcely become a
science, these phenomena were regarded with awe, as the
precursors of calamity. Sir Isaac Newton cast light on
their origin by his discoveries in refraction by crystals,
&e.; particular investigations were also made by Mar-
riotte and others; and these researches will probably
bear on weather prediction. The experience of the writer
is that change of temperature and often rain follow the
appearance of halos, and the like.

Many complex halos are sometimes seen accompanying
mock suns. The following cases are recorded by Dr.
Buchan. |

* Editors of newspapers often refer inquirers incorrectly to
astronomical treatises.