444 Chronicles of Science. [July, 



lumps, like so many little cumuli of cotton wool. On contemplating 

 this kind of phenomena, the Rev. author says that he cannot divest 

 himself of the opinion that the photosphere is really made up of 

 clouds, and that the luminous stratum is actually constituted like our 

 clouds, the only difference being that the clouds on the earth are of 

 watery drops or crystals, and in the sun they are of some other sub- 

 stance in a state of suspension in the transparent atmosphere of the 

 sun, like water in our own atmosphere. This opinion is enforced on 

 observing the dissolving part of a spot, which presents all the pheno- 

 mena of our cloudy sky ; there are the forms of cumuli, of cirri, of 

 strati, so perfectly equivalent to those of our earth, that sometimes the 

 aspect of our clouds and of the hind part of the spot in the field of 

 the telescope is exactly the same. What is very singular are the small 

 bits of luminous photosphere in the middle of the nuclei, of which there 

 is an example in the figure. The edge of the spot seems perfectly 

 comparable to the edge of the cumuli when in summer time they 

 flow to fill up the chasm which is in the centre or opening of the 

 cloudy stratum. 



This article of Father Secchi's brought forth a note from Sir J. 

 F. W. Herschel, Bart., stating that he does not think the willow leaves 

 are clouds in the ordinary sense of the word, he believes them to be 

 permanently solid matter, having that sort of fibrous or filamentous 

 structure which fits them when juxtaposed by drifting about and 

 jostling one against another to collect in blocks, as flue does in a room. 

 In answer to the question, Why are these, and these only, luminous ? 

 the author replies, Because they are solid and they float (at the level 

 determined by their density) in gaseous or transparent liquid, or inter- 

 mediate matter of immensely high temperature. The non-luminosity 

 of the medium in which they float being quite sufficiently accounted 

 for by supposing it of colourless transparency, colourless gases or 

 transparent liquids giving off no heat from their interior. This is, in 

 fact, the theory stated in Sir J. F. W. Herschel's article on Solar 

 Spots, published in our Number for April, 1864. 



The next communication consisted of a letter from Father Secchi, 

 on the spectrum of the Great nebula in Orion ; apparently not know- 

 ing that Mr. Huggins had already sent a paper on this subject to the 

 Royal Society, the Beverend Father hastens^to give the results which 

 he has met with. The whole spectrum of this nebula reduces itself to 

 three lines : one (a) tolerably strong, and which is seen wherever there 



is nebulosity ; the second (b) fainter ; and the third (c) stiU more 

 faint, and very near to (a). The group is situate between the Sodium 



