1887-88.] optical Phenomenon seen in G tenure. 16 [ 



the intention of meeting on the plateau shown on tlie 

 Ordnance Survey map at the 2000 feet level. This we 

 ultimately did. At this time — about 2 P.M. — thin mist was 

 covering the whole top of the mountain. We soon got into it 

 without our progress being impeded. Above 2250 feet the 

 ground was very rough, with large detached granite boulders, 

 but very little vegetation of any kind. At 3.15 P.M. we 

 gained the summit, and sat down to rest ourselves by the edge 

 of a precipice overlooking a corrie of great depth. The mist 

 had now nearly cleared away from the summit, but was being 

 driven in large masses into the corrie far below. All at once 

 we saw our shadows distinctly thrown by the sun on the 

 mist away down in the abyss, in the centre of a brilliant 

 triple circular rainbow, a small segment of which was cut 

 off by the edge of the precipice where we were sitting. This 

 phenomenon, which was new to all of us, appeared and 

 disappeared at short intervals several times, after which the 

 sun's light came out stronger than before, and it disappeared 

 altogether. The movements made by the party were of course 

 reproduced within this brilliant band of colour, the centre of 

 which appeared to be from 40 to 50 feet in diameter. There 

 was little wind at the time, but what there was, was blowing 

 in a circular manner, carrying the mist over the summit in 

 one direction, and up the valley leading to this corrie and over 

 an adjoining neck in exactly the opposite way. We were, of 

 course, considerably impressed with the spectacle, and noted 

 all the points as carefully as we could. At our President's 

 request I wrote a letter regarding this phenomenon to the 

 ' Scotsman,' and also asking whether in the Highlands these 

 occurrences were frequent. This letter appeared in the issue 

 of the 6th August last, but no replies were forthcoming. I 

 have been spoken to by a considerable number of people re- 

 garding this appearance, and have been told by most of them, 

 that " it must be quite common ; " but on asking the question, 

 as I invariably did, " Have yon seen such a thing ? " have as 

 often had " No " for an answer. 



Phenomena of this nature are classed together under the 

 name of Aiitlidia, from two Greek words meaning " opposite 

 to the sun," in contradistinction to those phenomena termed 

 Parhelia, meaning " near the sun." The most common of all, 



