400 Proceedings of the Rn?/al Society of Ed'tnlurgh. 



coarser food ; liis condition alters, and his flesh becomes soft 

 and tasteless. The stomach and intestines are found loaded 

 with putrescent remains, and gutted or unguttcd, this fisli could 

 never be brought into the market as equal to the product of the 

 Dutch fisheries. 



Feb. 4. — SiE Thomas Makdougall Brtsbaxe, President, 

 in the Chair. The following communication was read : — 



Account of some Optical Phenomena observed upon the 

 Rigi, on the 16th October 1832. By James D. Forbes, 

 Esq., r. K. SS. L. and Ed. 



The object of this paper, was to describe an example of a class 

 of phenomena, which is imperfectly understood. The author ob- 

 served an indistinct mass of reflected light, surrounded by a faint 

 glory, on the surface of a stratum of thick white clouds, 1000 or 

 1200 feet below him, when descending from the Rigi. The centre 

 of the coloured circle was the point diametrically opposite to the 

 sun, and consequently varied with the position of the observer. 

 As he approached the level of the cloudy ccean, the colours became 

 brighter, and the circle more distinctly formed, and the shadows of 

 the author and his companion were thrown with distinct outlines 

 upon the illuminated surface. The diameter of the red ring of the 

 corona was about 18°, and he ascertained, by experiment, that the 

 distance of the plane on which it was formed, was only 70 

 feet. The red occupied the interior of the prismatic circle. When 

 completely immersed in the cloud, the shadow of the observer as- 

 sumed a new appearance, owing to the want of a definite illumi- 

 nated surface upon which it could be thrown ; and the continua- 

 tion of the shadow towards the interior of the cloud, presented the 

 aspect of shadows when a sun-beam is admitted into an atmosphe- 

 ric space filled with light dust ; and, by the efl^ect of perspective, 

 gave an appearance of a true convergence of rays, such as is occa- 

 sionally observed on a great scale opposite to the sun. 



The author pointed out that the theory of the coloured rings 

 sugo'ested by Mr Fraunhofer is untenable. It supposes the in- 

 flexion of rays, by watery particles round the head of the observer, 

 whilst experience shews, that these eflfects are produced, when 

 the observer stands in a perfectly pure atmosphere, and even at 

 the distance of 1000 feet from the cloud. The theory of Dr 

 Young was also noticed, which presumes a quadruple reflection in 

 the interior of the aqueous drops ; an opinion which, perhaps, it 



