Variable Stars. 
4 ° 
[January, 
applied in special cases, they fail utterly in reconciling 
themselves with the nearly similar occurrences in other 
stars. 
There is a theory, however, by which all the phenomena 
with which I have dealt may be explained in a very simple 
manner. And not only has the theory I am about to propose 
the merit of explaining them satisfactorily, but it is founded 
wholly upon arguments drawn from analogy. And further, 
it shows also the sudden appearances of “ temporary” stars, 
and the changes — whether regular or irregular — which the 
variable stars undergo, to be due to the different workings of 
one cause. 
But it will be necessary, before proceeding, to notice 
briefly the appearances which some of these temporary stars 
have presented. 
I take first the celebrated star of 1572. This star was 
first observed by Tycho Brahe. It seems to have flashed 
suddenly into existence, shining with a light which was 
comparable to that of Venus in quadrature ; indeed for a 
considerable time it was visible in full sunlight at noon. It 
faded very rapidly, however, and finally disappeared, having 
been visible for very nearly seventeen months. It may be 
that this instance was but the reappearance of a variable 
star of long period ; for upon previous occasions temporary 
stars have been observed near this spot. The evidence is 
of too frail a character, however, to warrant any definite 
opinion. 
The only other instance which I shall use is that of the 
outburst of a star, in the year 1866, in the constellation of 
Corona. This appearance was noteworthy because a spec- 
troscopic examination conclusively showed that its sudden 
accession of brilliancy was caused by an outbreak of hydro- 
gen, making it, as Prodtor remarks, fully 800 times brighter 
than it now is. Like the other, this star gradually faded, 
the hydrogen apparently cooling at the same time. 
Both these stars were situated close to the Milky Way. 
We shall see presently that this circumstance is highly sig- 
nificant. 
Now it seems to me that if we regard all the changes 
which take place in the light of the celestial orbs to be 
caused by meteors, we shall have made a decided advance 
upon former theories. Take first the case of Algol. If, in- 
stead of assuming that this orb is circled by a planetary 
orbit of the proper eccentricity, we assume that he is sur- 
rounded by extensive meteor systems, we have, certainly, a 
thoroughly practical and analogical way of escape from the 
