ined stage. However this may be
this line of research throws an instructive light on what we may expect
to find in the evolution of real stellar systems.

In the second part of this paper I shall point out the bearing which
this investigation of the evolution of an ideal liquid star may have on
the genesis of double stars.

II.

There are in the heavens many stars which shine with a variable
brilliancy. Amongst these there is a class which exhibits special
peculiarities; the members of this class are generally known as Algol
Variables, because the variability of the star Beta Persei or Algol was
the first of such cases to attract the attention of astronomers, and
because it is perhaps still the most remarkable of the whole class. But
the circumstances which led to this discovery were so extraordinary that
it seems worth while to pause a moment before entering on the subject.

John Goodricke, a deaf-mute, was born in 1764; he was grandson and heir
of Sir John Goodricke of Ribston Hall, Yorkshire. In November 1782,
he noted that the brilliancy of Algol waxed and waned (It is said that
Georg Palitzch, a farmer of Prohlis near Dresden, had about 1758 already
noted the variability of Algol with the naked eye. "Journ. Brit. Astron.
Assoc." Vol. XV. (1904-5), page 203.), and devoted himself to observing
it on every fine night from the 28th December 1782 to the 12th May 1783.
He communicated his observations to the Royal Society, and suggested
that the variation in brilliancy was due to periodic eclipses by a dark
companion star, a theory now universally accepted as correct. The
Royal Society recognised the importance of the discovery by awarding to
Goodricke, then only 19 years of age, their highest honour, the Copley
medal. His later observations of Beta Lyrae and of Delta Cephei were
almost as remarkable as those of Algol, but unfortunately a career of
such extraordinary promise was cut short by death, only a fortnight
after his election to the Royal Society. ("Dict. of National Biography";
article Goodricke (John). The article is by Miss Agnes Clerke. It is
strange that she did not then seem to be aware that he was a deaf-mute,
but she notes the fact in her "Problems of Astrophysics", page 337,
London, 1903.)

It was not until 1889 that Goodricke's theory was verified, when it
was proved by Vogel that the star was moving in an orbit, and in such
a manner that it was only possible to explain the rise and fall in the
lu