, 1912-03-30

S RAY FROM sun. r REFRAcT1oNs. G COLOURS,
This simple experiment shows us that
light is complex, being made up of many
differently coloured rays, each having It's
OWE c~apability of being refracted, the red
being refracted the least, the violet the most.
Nature using other means, shows us the
same thing in the rainbow.
In a general way we can now understand
how there can be ice-crystals high III the ar,
and how these being prisms can change the
direction of the suns light which falls on
them and also show the colours of the rain
bow. The further details are too compil-
Gated for introduction here, but we give
some of the facts. Professor LOOMS says
that the inner circle has a radius of about
~ degrees (about a quarter of n right an
gle). The sky inside the halo is dark and
the halo itself is red on the inside and pale
blue on the outside. The outer circle is
similar to the inner, but has q radius of ~ deg.
(about half n right angle). The interval be-
tween the two circles is dark, but not so
much so as the space within the inner
circle.
The extent of the country over which in
any given case the ha'os are seen depends
mainly on the extent of The cloud sheet of
ice crystals. The light shines through diff
ferent parts of the cloud at different places,
and, although the same rales prevail every
where, each place has its own halo; in
fact every observer has his own. Ia the
case under consideration the halos were
seen from both our towns. AS the pre-
sent writer saw them only about half
of each was visible, but that was partly
due TO the presence of many low clouds. In
Frederiksted Mr. Jean Petersen saw the in
ner halo complete, the outer one with the
upper half wanting. He also saw Il white en-
Gle passing through the sun and out III an up
yard direction to about where the larger halo
would have reached had it been complete.
Professor Loomis gives the following account
Of this kind of circle. He writes: "When n
halo is formed round the sun we often no.
tice q white circle passing through the sun
aud parallel to the HORIZON. This is called
a Parhelic circle, aud is produced by the
reflection Of the suns light from the prisms
or snow crystals whose surfaces have a YER
tical position. When the air is tranquil the
flakes Of snow which are present iii the ut
mOsphere descend slowly to the earth. and
they tend to assume that position in which
they experience the least resistance from
the air. For most forms of SNOW flakes,
this position will be when the principal faces
of the crystal are perpendicular to the
horizon, aud the light of the sun may
reach the eye reflected from such snow
Fl lkes as are situated on a horizontal Cir
Gle passing through the sun. This circle
never exhibits p%rismatic colours like the
aforementioned halos."
Halos are commonly supposed to %foretell
rainy or windy weather. Sometimes they
do but the weather depends upon 50 many
conditions that no single condition can be
relied on to ~foretell anything. Hence halos,
whether around the sun or AROUND the moon,
cannot be taken as telling more than that
The light at the time is passln9 through clouds
formed of ice crystals.
AT 3 p. m. on Saturday last a meeting of
the Agricultural Society was held at the Ex-
pertinent Station, on the invitation of the