420 ANNUAL OF SCIENTIFIC DISCOVERY. 



ruption of the luminous envelope to be itself an evidence of its compcirative 

 thinness. He considers that the faculoc are only the crests of parts of the 

 photosphere which arc elevated above the general level. According to this 

 hypothesis, the faculoj are only more luminous relatively to the darker por- 

 tions near the edge of the solar disk. Furthermore, he has arrived at the 

 conclusion that the penumbra of a spot near the centre, seen with a feeble 

 power, docs not appear in reality to be blacker than the portions of the disk 

 near the edge, the light from which is little more than half that of the bril- 

 liant central parts. From this he infers that the lower strata of the solar 

 atmosphere must exert an enormous power of absorption, and produce a 

 great diminution of light in the interior of the cavity formed by the photo- 

 sphere. Lastly, Father Sccchi has established, in a manner satisfactory to 

 himself, from drawings of the positions and form of numerous spots, that 

 the greater number of the faculse show themselves in the regions where the 

 spots appear, namely, above and below the equatorial zone. There is, 

 therefore, reason to suppose, that, compared with the tropical regions, the 

 solar equator enjoys a degree of calm similar to that which exists in the 

 corresponding part of the terrestrial atmosphere. This latter fact agrees 

 admirably with the observations of Carrington, who was the first to notice 

 the motion, in opposite directions, of the spots situated above and below the 

 solar equator. Father Sccchi considers that the influence of the spots is 

 towards raising the temperature of the earth. 



MAXWELL'S THEORY OF SATURN'S RINGS. 



Prof. Maxwell, of England, in a recent treatise on the stability of the 

 motion of Saturn's rings, which gained the Adams prize at Cambridge in 

 1836, gives us the following as the result of his investigations of the subject: 



" The result of the mechanical theory is, that the only system of rings 

 which can exist is one composed of an indefinite number of unconnected 

 particles revolving round the planet with different velocities, according to 

 their respective distances. These particles may be arranged in series of 

 narrow rings, or they may move through each other irregularly. "We are 

 not able to ascertain by observation the constitution of the two outer divis- 

 ions of the system of rings ; but the inner ring is certainly transparent, for 

 the limb of Saturn has been observed through it. It is also certain that, 

 though the space occupied by the ring is transparent, it is not through the 

 material parts of it that Saturn was seen, for his limb was observed Avithout 

 distortion; which shows that there was no refraction, and therefore that the 

 rays did not pass through a medium at all, but between the solid or liquid 

 particles of which the ring is composed. Here, then, we have an optical 

 argument in favor of the theory of independent particles as the material of 

 the rings. The two outer rings may be of the same nature, but so ex- 

 ceedingly rare that a ray of light can pass through the whole thickness 

 without encountering one of the particles." 



