16 Transactions of the 



evidently a solar phenomenon, indicates the existence of a belt of luminous 

 matter, or of matter that may become luminous, extending around the sun, 

 even outside the earth's orbit. 



Next in order may be mentioned the interesting relation recently shown 

 to exist between some of the comets and the periodic meteors. Thus, Tem- 

 pel's comet of 1865, and the November meteors, are said to have the same 

 orbit ; that is to say, the orbits are so nearly identical that they indicate a 

 common origin. In a similar way it is found Tuttle's comet of 1862 moves 

 along in company with the August meteors, and the bright comet of 1861 

 moves in company with a less conspicuous group of April shower-meteors. 

 Oppolzer, Peters, Weisse, Le Verrier and others have contributed to these 

 results; but Schiapparelli, of Milau, has been the most active, both in 

 obtaining results and in interpreting them, and his theory is favorably 

 received. Nebulse is a name given to bodies of cosmical matter in that 

 diffuse condition in Avhich it is supposed the material of the solar system once 

 existed, when it occupied continuously all the space from its center far 

 beyond the limits of Neptune's orbit. Schiapparelli supposes that among 

 such cosmical clouds, floating in space, it occasionally happens that one 

 comes within reach of the sun's attractive influence. The attraction acts 

 more powerfully on the nearer portion, and while the nebula is still at a 

 great distance, it begins to lose its spherical form, becomes elongated and 

 somewhat cylindrical, the foremost part becoming denser and more pointed. 

 As it approaches nearer the sun the transformation becomes more complete, 

 the part nearest the sun becoming a dense nucleus, and the part following 

 forms the tail, curved in consequence of the lateral motion preserved by the 

 nebula during its progress. 



Thus we have a comet moving in an orbit whose eccentricity and plane 

 depend upon the initial circumstances. The comet is not, however, a solid 

 mass, but consists of particles, each possessing an independent motion, and 

 the comet becomes more elongated, and at last is resolved into a ring of 

 meteors. In the course of time the matter composing a comet, which com- 

 pletes its revolutions around the sun, must be dispersed over the whole path. 

 Schiapparelli affirms that the comet of 1862, No. Ill, is simply the remains 

 of the original comet, out of which the meteoric ring of the 10th of August 

 has been formed in the course of time. Le Verrier, adopting this theory, 

 traces the history of the comet of 1866, No. 1, first discovered by Tempel. 

 A cosmical nebulous cloud he thinks entered our system in January, 126, 

 and happening to pass near the planet Uranus was brought by its attraction 

 into an elliptic orbit around the sun. This orbit is that of Tempel's comet, 

 and identical with that of the group of November meteors. He supposes 

 this meteoric cloud became visible as a comet in 1866 for the first time. 

 The tail of this comet is composed of the multitude of small meteoric bodies 

 which follow the nucleus, and as our earth encounters them for three success- 

 ive years, the tail must have a length of nearly eighteen hundred millions 

 of miles. Such, in brief, is the theory of comets and their tails, as advocated 



