>BY CAPT. F. W. L. THOMAS, R.N.
30th May 1861 – Noon: left Loch Tarbert, Harris.
8 P.M. it fell calm when we were four miles from Rodel, Harris.
There were a few trifling showers, and the air was beautifully clear.
At 8.15, when the sun’s altitude was about ten degrees, a brilliant rainbow (C) formed; – its estimated altitude was 40 degrees.
Where the arch joined the horizon (A B) its colours were very bright.
A secondary bow (D) also formed, with the usual characteristics.
But, what must be very unusual, a third or extraordinary bow – (E) appeared.
The extraordinary and primary bow arose from the same points of, and were coincident with, the horizon; from whence the legs of the extraordinary bow rose almost perpendicularly, but bending gradually into a broad elliptic arch, whose summit, estimated at 70 degrees of altitude, was above that of the secondary bow.
The colours of the extraordinary bow were in primary order; less bright than the primary, but brighter than the secondary bow.
Neither the summits of the secondary nor extraordinary bows were ever very distinct.
The phenomenon lasted about half an hour.
A sketch of the arrangement is here drawn. (Please see embedded page)
Note: An old sailor informed me that he once witnessed a similar appearance of rainbows in the West Highlands. And in the Enc. Met. Mety., p. 171, is quoted a description of a like phenomenon, seen by Dr Halley from the walls of Edesten; but in which the extraordinary bow contracted until the upper portion of the arch became coincident with the upper portion of the secondary bow, when, from the order of the colours being contrary, the blending of the two produced white light.
Source: Journal of the Scottish Meteorological Society, Volume 1, Nos I-XII, 1866. p270
Note: He had completed surveying ‘East Loch Tarbert’ 4 years earlier, and the West Coast from the ‘Sound of Harris to Lochs Tarbert & Resort’ in1860, so the precise purpose of this voyage is uncertain we can be sure that Fred Thomas had been putting the time to good use, perhaps even collecting Webs with his wife?