378 On a Temporary Outburst of Light | July, 
Riccio, in 1651, extended the Chaldean hypothesis of the 
moon to the temporary stars, and suggested that these objects may 
be luminous on one side only. ‘The variation in their brilliancy 
might, he supposed, be produced by a rotation about an axis. The 
intermittent light of some of our modern lighthouses may be men- 
tioned as an illustration of this theory. Riccioli added, “ When the 
Deity wishes to exhibit to mankind any extraordinary sign, he 
makes one of these stars turn rapidly upon its axis.” 
In modern days the opinion seems to have been growing that 
the new stars of history may be the periodic maxima of permanent 
but extremely variable stars. M. H. Goldschmidt has brought 
together reasons to show that the new stars of a.p. 393, 827, 
1203, and 1609 were probably periodic outbursts of light in one 
and the same star. 
In a recent work of considerable interest,* Dr. J. C. Zéllner 
endeavours to explain the phenomena of the heavens in accordance 
with the hypothesis of a nebulous origin of the universe. He sup- 
poses that a fiery mass in the process of cooling would become sur- 
rounded with a crust of cooled matter. He conceives further that 
the sudden bursting of this external crust and the outflow of glowing 
matter from within might present appearances not unlike those fur- 
nished by the temporary stars. 
Thanks to the researches of Kirchhoff and others we now pos- 
sess a method of analyzing the nature of a distant source of light, 
which, it might be expected, would give to us some information of 
the true condition of the enormous changes which must be taking 
place in these stars of ephemeral lustre. The observations of the 
writer and his distinguished colleague, Dr. W. A. Miller, have 
shown that matter of a nature common to that of our system, and 
subject to physical laws similar to those which prevail on the earth, 
exists throughout the stellar host. It was therefore to be expected 
that the phenomena of the temporary stars were due to physical 
changes, of which the precise nature might be revealed by prismatic 
examination. 
It has been the good fortune of the writer, conjointly with Dr. 
W. A. Miller, to examine the spectrum of a bright star, which 
during the past month suddenly burst forth in the constellation of 
the Northern Crown. 
The sudden outburst of light in this star appears to have been 
first seen by Mr. John Birmingham, of Tuam, on the 12th of May. 
In a letter to the writer, Mr. Birmingham describes the star as 
appearing on that evening “ very brilliant, of about the 2nd mag- 
nitude, certainly more brilliant than « Corone.” 
* «Photometrische Untersuchungen mit besonderer Riicksicht auf die Physische - 
Beschaffenheit der Himmelsk6rper.’ Leipsig, 1865. 
