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Concerning reflection rainbows
I have not seen a reflection bow ( I live in the middle of a big city,
London). But I keep my eyes peeled. You never know; it rains here and we
have a large river (the Thames) running through the middle of the city. I
did once see a beautiful bow spanning the river as I crossed it in a
train, but no reflection bow. I assume that the reflecting body must be
large enough to have the same physical size as the bow. i.e. a small pond
won't do, nor will a river if the sun is shining along its length, rather
than at right angles to it.
A few years ago I spent some time looking up historical accounts of
rainbows. The earliest account of a reflection bow I came across was by
Edmond Halley, the English scientist. 50 years later, Anders Celcius, the
Swedish scientist, reported seeing a similar bow. There are also several
accounts of reflection bows in the early years of the scientific magazine
NATURE. Many of the sightings were made in Scotland, which seems to have
an ideal combination of low sun, rainy climate and many lakes.
By the way, Halley (a particular hero of mine) was one of the great
skywatchers of history, and the Philosophical Transactions of The Royal
Society published many of his letters about the rainbows and halos that he
saw in his travels.
Unfortunately, few scientific journals these days have room for such
apparently trivial matters as sharing rainbow or halo spotting with
others, so this mailing list is a godsend to us skywatchers.
As for the reflection rainbows:
Halley saw a reflection primary from the city walls of Chester, a town
near Liverpool, England, in August 1697. He published an account of it
(see the Philosophical Transactions of May 1698 for the full text and a
drawing.)
Here is the relevant bit of what he saw:
"On the 6 th day of August last, in the evening, between six and seven of
the clock, I went to take the air upon the walls of Chester, when I was
surprised by a sudden shower, which forced me to take shelter in a nich
that afforded me a seat in the wall, near the NE corner thereof. As I sat
there, I observed an IRIS, exceedingly vivid, as to its colours, at first
on the south side only, but in a little time with an entire arch; and soon
after, the beams of the sun being very strong, there appeared a secondary
IRIS, whose colours were more than ordinary bright, but inverted, as
usually that is, the red was inward, which in a primary IRIS is outside,
and e contra for the blues. But what I took most notice of was, that with
these two concentric arches there appeared a third arch, near upon a
bright as the secondary iris, but coloured in the same order of the
primary, which took its rise from the intersection of the horizon and the
primary iris, and went cross the space between the two, and intersected
the secondary..."
Anders Celsius reported seeing a reflection bow in central Sweden in 1743,
an account of which was published in Histoire de L'Academie Royale Des
Sciences (1743, pp 35): Here is the relevant section
"...It is to be noted that according to the observer [Anders Celsius] the
distance to the top of this more than semi-circular eccentric arc, was as
far above the top of the secondary arc as the secondary arc is above the
primary one; that its colours were more or less equally bright throughout
the length of its arc as those of the secondary bow becoming washed-out,
indistinct and confused where it intersected the secondary arc and on the
horizon with the primary one, and that it lasted at the very most a
quarter of an hour."
Apologies for the length of this, but someone out there may find this
interesting.
Cheers!
John
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