1864. | Astronomy. 447 
subject of solar spots. At Ely, a large refractor of 6 inches aperture 
has been got into working order, and we may soon expect to hear 
that Mr. Titterton has succeeded in obtaining, by its means, solar 
autographs of 6 inches diameter. 
The discussion on the phenomena in the solar envelopes, com- 
menced by Mr. Nasmyth, is still occupying great attention, A 
question has arisen whether the general appearance of the photo- 
sphere is that of a flocculent precipitate, as suggested by Sir John 
Herschel, and assented to by Dr. Dawes, or whether it more nearly 
resembles a willaw-leaved. crystalline precipitate of detached particles, 
as originally described by Mr. Nasmyth and confirmed by Mr. De la 
Rue and Mr. Pritchard; and more lately Mr. Stone, with the large 
Greenwich refractor, has confirmed the existence of these strange 
entities, which to him appear like grains of rice. Although indi- 
vidual observers may therefore differ among themselves as to the 
exact shape of these particles, there appears to be no doubt that the 
sun’s photosphere is covered with solid bodies, the immediate origin 
of the solar light, somewhat uniform in size and shape, the smallest 
of them having an area exceeding that of the British Isles! 
Magnus * has lately recorded an experiment which, whilst it sup- 
ports the lately propounded theory of Kirchhoff, on the constitution of 
the sun, in a striking manner, also appears to be quite concordant with 
the “ willow-leaf” discoveries. It is well known that when a non-lumi- 
nous gas-flame has a sodium compound introduced into it, the whole 
flame becomes brilliantly luminous with yellow light. Similarly, if 
lithium, strontium, or other metallic compounds are introduced into 
the flame, brilliant light of other colours is evolved. Now, Magnus has 
shown that the radiation of heat is also increased when these metallic 
vapours are rendered incandescent in the flame. The experiment 
was so arranged that a fixed spot in the soda flame was always com- 
pared with the same spot in the non-luminous flame, and care was 
also taken that the heat from the solid soda introduced into the fiame, 
or from the platinum-wire which held it, could not radiate against 
the thermo-pile which served for the observation. The luminous 
flame radiated about a third more heat than when it was non- 
luminous. When, instead of soda vapour, a solid body, such as 
platinum, was brought into the portion of the flame experimented 
upon, a still greater radiation of heat occurred, and when the plate 
was covered with carbonate of soda the radiation increased afresh, 
and by keeping the flame likewise luminous with soda vapour the 
radiation of heat was increased three-fold. These experiments show 
that gaseous bodies radiate very much less heat than solids or liquids ; 
it can therefore hardly be maintained that a gaseous or vaporous 
photosphere is the seat of the solar heat. The luminous- and heat- 
radiating particles in the yellow gas flame are therefore probably 
single torn-off particles of solid (or liquid) matter incandescent in the 
flame, and, comparing great things with small, they may be regarded 
as the counterparts of the willow-leaf particles in the solar envelope. 
* *Poggendorff’s Annalen,’ No. 3, 1864 ; and ‘ Phil. Mag.,’ May, 1864. 
