ADDRESS. 2 9 



To examine the spectrum of a shooting star would seem even more 

 difficult. Alexander Herschel first succeeded in doing so, and determined 

 the presence of sodium ; since which Von Konkoly has recognised the 

 lines of magnesium, carbon, potassium, lithium and other substances, and 

 it appears that the shooting stars are bodies similar in character and com- 

 position to the stony masses which sometimes reach the earth as aerolites. 



Some light has also been thrown upon those mysterious visitants, the 

 comets. The researches of Prof. Newton on the periods of meteoroids led 

 to the remarkable discovery by Schiaparelli of the identity of the orbits 

 of some meteor-swarms with those of some comets. The similarity' of 

 orbits is too striking to be the result of chance, and shows a true cos- 

 mical relation between the bodies. Comets, in fact, are in some cases at 

 any rate groups of meteoric stones. From the spectra of the small comets 

 of 1866 and 1868, Huggins showed that part of their light is emitted by 

 themselves, and reveals the presence of carbon in some form. A photo- 

 graphic spectrum of the comet recently visible, obtained by the same 

 observer, is considered by him to prove that nitrogen, probably in com- 

 bination with carbon, is also present. 



No element has yet been found in any meteorite, which was not 

 previously known as existing in the earth, but the phenomena which they 

 exhibit indicate that they must have been formed under conditions very 

 different from those which prevail on the earth's surface. I may mention, 

 for instance, the peculiar form of crystallised silica, called by Maskelyne, 

 Asmanite ; and the whole class of meteorites, consisting of iron generally 

 alloyed with nickel, which Daubree terms Holosiderites. The interesting 

 discovery, however, by Nordenskiold, in 1870, at Ovifak, of a number of 

 blocks of iron alloyed with nickel and cobalt, in connection with basalts 

 containing disseminated iron, has, in the words of Judd, ' afforded a very 

 important link, placing the terrestrial and exti'a-terrestrial rocks in closer 

 relations with one another.' 



We have as yet no sufficient evidence to justify a conclusion as to 

 whether any substances exist in the heavenly bodies which do not occur 

 in our earth, though there are many lines which cannot yet be satisfac- 

 torily referred to any terrestrial element. On the other hand, some 

 substances which occur on our earth have not yet been detected in the 

 sun's atmosphere. 



Such discoveries as these seemed, not long ago, entirely beyond 

 our hopes. M. Comte, indeed, in his ' Cours de Philosophie Posi- 

 tive,' as recently as 1842, laid it down as an axiom regarding the 

 heavenly bodies, that ' Nous concevons la possibilite de determiner leurs 

 formes, leurs distances, leurs grandeurs et leurs mouvements, tandis que 

 nous ne saurions jamais etudier par aucun moyen leur composition 

 chimique ou leur structure mineralogique.' Yet within a few years 

 this supposed impossibility has been actually accomplished, showing how 

 unsafe it is to limit the possibilities of science. 



It is hardly necessary to point out that, while the spectrum has taught 



