450 The Fuel of the Sun. [October, 



that envelopes the photosphere, will radiate more freely, 

 its dissociated matter will combine more abundantly, 

 and will thicken the photosphere immediately below ; 

 this thicker flame will be more luminous than the 

 normal surface, and thus produce the phenomena of the 

 faculce. 



Besides these great ground-swells of the flaming ocean of 

 the photosphere, there must be lesser billows, and ripples 

 upon these, and mountain tongues of flame all over the 

 surface. The crests of these waves, and the summits of 

 these flame-alps, presenting to the terrestrial observer a 

 greater depth of flaming matter, must be brighter than 

 the hollows and valleys between ; and their splendour 

 must be further increased by the fact, that such upper 

 ridges and summits are less deeply immersed in the outer 

 ocean of absorbing vapours, which limits the radiation of 

 the light as well as the heat of the photosphere. The effect 

 of looking upon the surface of such a wild fury of troubled 

 flame, with its confused intermingling of gradations of 

 luminosity, must be very puzzling and difficult to describe ; 

 and hence the " willow leaves," " rice grains," " mottling," 

 "granules," "things," "flocculi," " bits of white thread," 

 " cumuli of cotton wool," " excessively minute fragments 

 of porcelain," "untidy circular masses," "ridges," "waves," 

 " hill knolls," &c, &c, to which the luminous irregularities 

 have been compared. 



At the time I wrote, the means of examination of the 

 edge of the sun by the spectroscope was but newly dis- 

 covered, and the results then published referred chiefly to 

 the prominences proper. Since that, a new term has been 

 introduced to solar technology, the " sierra," and the obser- 

 vations of the actual appearances of this sierra precisely 

 correspond to my theoretical description of the limiting 

 surface of the photosphere, which was written before I was 

 acquainted with these observed facts. This will be seen by 

 reference to chapter 10, the subject of which is, "The 

 Varying Splendour of Different Portions of the Photo- 

 sphere." 



But I must not linger any further upon this part of the 

 subject, but proceed to another, where subsequent dis- 

 coveries have strongly confirmed my speculations. 



The mean specific gravity of the sun is not quite ij times 

 that of water. The vapours of nickel, cobalt, copper, iron, 

 chromium, manganese, titanium, zinc, cadmium, aluminium, 

 magnesium, barium, strontium, calcium, and sodium have 

 been shown by the spectroscope to be floating on the outer 



