312 Intelligence and Miscellaneous Articles. 



On page 304 of vol. xci. lie states that he uses the term self-lumi- 

 nous clouds " as a general expression for all phenomena of the 

 sun, in what shape soever thej^ may appear, that shine by their 

 own light." 



On page 287, referring to the " corrugations " all over the sur- 

 face, which he considered to consist of elevations and depressions, 

 he quotes some of his observations as follows : — 



M Dec. 22, 1799. The whole disc of the sun is strongly indented. 



"Dec. 23, 1799. The corrugations have a mottled appearance. I 



see the figure of the dark and bright places. Many of the dark 



places are not round, but a little extended in different directions, 



and appear to be lower than the bright places. 



"Dec. 27, 1799. On examining some of the largest corrugations 

 with a high magnifying power, I see plainly that the less bright parts 

 or indentations are small openings, and that those dark places which 

 are the coarsest show the opake surface of the sun the best." 



In another place he remarks, "The whole disc is very much 

 marked with roughness like an orange. Some of the lowest parts 

 of the inequalities are blackish." 



"Jan. 31, 1800. The indentations are very uniform, but not 

 round. It seems they admit of every possible shape. 



"Feb. 4, 1800. The points, or rather darker-coloured places in 

 the punctulations, were of different figures, few of them being 

 round. 



"Feb. 18, 1800. Among all the corrugations, I could hardly 

 perceive any that were round. They were of all shapes, chiefly 

 lengthened. 



"Jan. 15, 1801. The low places of corrugations do not contain 

 punctures, but seem to be irregularly shaped places of less luminous 

 matter than the borders which inclose them." 



On these passages it may be remarked that the decided mention 

 of pores or punctures on some occasions, and the statement on 

 others that there were none to be seen, strongly supports the con- 

 clusion I have arrived at, that the visibility of these minute dark 

 points is subject to great variation. 



Though Sir William seems to have entertained no doubt that the 

 less luminous portions of the photosphere were considerably depressed 

 below the brighter parts, yet he states that they were visible in every 

 part of the disc, and in one place observes, under date Dec. 20, 

 1794, " I can follow the indentations from the centre up to the mar- 

 gin of the sun ; but it requires great attention, as, on account of the 

 sphericity of the disc, they become gradually less conspicuous the 

 nearer we go to the circumference. I saw them equally well at the 

 north pole of the sun." 



As I have before remarked, the depression must be extremely small 

 for this to be the case ; and I should be far more inclined to attri- 

 bute the increased difficulty in making out the spaces of different 

 luminosity to the great fore-shortening of both near the sun's edge, 

 though they might be on the same level. — From the Monthly Notices 

 of the Royal Astronomical Society , January 8, 1864. 



