THE NEW STAR IN THE MILKY WAY. 545 



the other, according as the body which contained dark lines in 

 its spectrum was approaching the earth or receding from it. 



After this very brief statement of general principles, we can 

 now refer to the observations that have already been made with 

 regard to the spectrum of the present new star, observations 

 unique in astronomical history, and of the highest importance 

 and interest. It has been found to consist of both light and dark 

 lines. The fact that pairs of bright and dark lines are seen proves 

 that two bodies are in question. If we suppose two swarms of 

 meteors colliding in space, the spectrum can be easily explained 

 on this assumption in the light of the general principles referred 

 to above. Further, the thickness of the lines tends to show that 

 each one is produced by a large number of small incandescent 

 masses moving at different velocities, rather than by one large 

 one. The motion necessary to produce the doubling of these lines 

 has been estimated, and the relative velocity of the two swarms 

 has been put down as more than five hundred miles per second ! 



If the photographs should continue to show the same relative 

 positions of the bright and dark lines, the observations would 

 prove that this relative motion is not produced by the revolution 

 of one body round another, but that a dense swarm of meteorites 

 is moving toward the earth with a high velocity, and passing 

 through another receding one of less density. 



It will be seen that the observations harmonize well with the 

 hypothesis that has been advanced on much less definite evi- 

 dence ; but this is not the only instance we can give of the grip 

 that modern science has on large classes of phenomena which 

 were supposed to be beyond the reach of man. The lines that 

 have been photographed in the spectrum of this star are all 

 such as could have been predicted with our knowledge of new 

 stars. 



As an instance of the advanced stage at which astro-physical 

 science has arrived, we may say that, if we had no observations 

 of new stars other than those already recorded of the present one, 

 their whole theory could be obtained by induction. This may 

 seem a " sweeping statement," but it is nevertheless true, for since 

 many so-called "stars" are now known not to be "stars" like 

 our sun, but simply clouds of meteoritic bodies clashing togeth- 

 er, and since we know approximately the sequence of changes 

 through which the spectra of these stars pass as their tempera- 

 ture is first increased and then reduced, each spectrum indicates 

 the complexity of each swarm. 



We have already seen that the doubling of the bright and 

 dark lines indicates that we are dealing with two swarms in the 

 present instance, one approaching and the other receding; we 

 now learn that the condensation at which each of these swarms 



VOL. XLII. 36 



