114 F. W. Very — A Cosmic Cycle. 



given by destruction of motion through impact would be high, 

 and in this respect Lockyer's meteoritic hypothesis, as applied 

 by him to the novge, agrees with the facts. Moreover, this 

 intense incandescence is immediately followed by a rapid 

 refrigeration which demonstrates that the subsequent history 

 is that of the cooling of relatively small masses. K single body 

 of solar dimensions, raised to a temperature of the same order 

 as that of the sun by a collision, or by any other mode, could 

 not cool to invisibility in a few days. The flaming out of a 

 nova is sudden. Its subsequent fading and passage to a nebula, 

 or to invisibility, is to be attributed, on Lockyer's hypothesis, 

 to the recession of the colliding swarms ; and the cessation of 

 high-speed impacts, together with the retention, at least for a 

 time, of internal disturbances due to the previous collision, 

 seems competent to explain the nebulous illumination. But 

 there is no place in this scheme for the actual sequence of 

 spectral changes. If produced by the meeting of meteor- 

 swarms, the nova ought to begin as it ends. The first collisions 

 of sparsely distributed outlying members of the swarm should 

 give a spectrum of bright lines ; these should- increase in bril- 

 liancy, the continuous spectrum and greatest intensity occurring 

 near mid passage, while the densest parts of the swarm are in 

 mutual collision. The sequence is entirely different, and points 

 to a sudden liberation of imprisoned forces, and to control 

 from a fixed center, the relative velocities being none at all at 

 first, but increasing to extraordinary proportions at the height 

 of the episode. There may have been a meteor-swarm anterior 

 to the nova, but, if so, it had already condensed, and it was a 

 single body. It is possible that the darkness of a nova, before 

 the outburst of intense light, may be caused by dense swarms 

 of relatively cold meteors which have not yet coalesced with 

 their primary, and which obstruct its light until dissolved in the 

 final blaze. 



The spectral relations of the new stars are with the bright- 

 line helium stars, with which the "Wolf-Rayet stars are con- 

 nected through the spectrum of the principle example, y Argus,* 

 which, in addition to hydrogen and helium (either dark, bright, 

 or doubly reversed), shows Rydberg's principal line of the 

 supposed new or proto-hydrogen spectrum in the blue at 

 A=4688, bright and with a breadth of 20 tenth -meters, also a 

 very bright blue band of unknown origin at X =4655, with a 

 breadth of 30 tenth -meters. 



*See F. McClean, Proc. R. S. London, vol. lxii, p. 419, 1898. 

 [To be concluded.] 



