VOL. XXIII.] PHILOSOPHICAL TRANSACTIONS. 663 



where s is the true sun ; z the zenith ; stpp a large white circle passing through 

 the sun, and, as near as I could judge, parallel to the horizon. It was very 

 distinct and entire, about two deg. broad in the northern part about t ; and held 

 much the same breadth in the east and west, but grew narrower towards the 

 sun : its edges were not very well defined, the whole appearing like a faint white 

 cloud, and a part of it would have been taken for such, but the whole circle, 

 seen in the pure azure sky, was a very extraordinary sight. 



VNXY is a halo, or rather iris, that was also an entire circle, having the sun 

 for its centre. I measured the semidiameter of this, which was about 22 deg. 

 the breadth of this arch, which was well defined, was by estimate equal to the 

 sun's diameter, and it was coloured with the colours of the iris, but by no 

 means near so vivid as in the common rainbow. The red colours were next the 

 sun, and the blue in the outer limb. Within this circle the sky appeared some- 

 what obscure, especially near the arch ; and I suppose the cause of that obscu- 

 rity was likewise that which made the sun shine so faint and waterish. I ex- 

 pected two parhelia at x and y in the intersections of this with the white circle, 

 having often seen them at that distance and position from the true sun, but at 

 this time none such appeared, 



vvp is an arch of another circle, of which only the upper part appeared ; it 

 was in all respects, both for breadth and colours, like the circle vnxy, which it 

 touched in the vertical point v, but its centre was below at n, or near it. In 

 the intersections of this arch with the white circle on both sides, there were 

 two very bright parhelia, which were also tinged with colours, especially on the 

 side next the sun, where they were very red. I measured their distance from 

 the true sun, and found it 31-r deg. About v, where the two arches were coin- 

 cident, it was very bright also, and the red on the inside very strong ; but the 

 species of the sun was there drawn out so in length that it could not properly 

 be called a parhelion ; this arch pvp boke off on both sides, about 5 or 6 deg. 

 below the parhelia pp. 



At N, or the lower part of the circle vnxy, there appeared also a small piece 

 of an arch, which touched it there, after the same manner as pvp touched in 

 V ; it seemed to have its centre in v, and about n there appeared another 

 longish red species, such as at v, but not quite so bright. 



The height of the sun, during the observation, was from 40 to 45 deg. 

 when clouds interposing, no more was to be seen ; the weather was cooler than 

 ordinary, with a gentle N. W. wind. And it was plain that the vapour which 

 caused this appearance, was higher than the clouds, for they were seen to drive 

 under the circles. 



VOL. IV. 4 Q 



