assigned by some astronomers to the presence of an opaque secondary,
which transits Algol at regular intervals; others have adopted the view
that Algol is a luminous secondary, revolving around an opaque primary.
Of these views the former seems the most natural and satisfactory. It
points to a secondary whose mass bears a far greater proportion to that
of the primary, than the mass even of Jupiter bears to the sun; the
shortness of the period is also remarkable. It may be noticed that
observation points to a gradual diminution in the period of Algol's
variation, and the diminution seems to be proceeding more and more
rapidly. Hence (assuming the existence of a dark secondary) we must
suppose that either it travels in a resisting medium which is gradually
destroying its motion, or that there are other dependent orbs whose
attractions affect the period of this secondary. In the latter case the
decrease in the period will attain a limit and be followed by an
increase.

However, interesting as the subject may be, it is a digression from
telescopic work, to which we now return.

Within the confines of the second map in Plate 4 is seen the fine star
[gamma] Andromedæ. At the hour of our observations it lies high up
towards E.S.E. It is seen as a double star with very moderate telescopic
power, the distance between the components being upwards of 10"; their
magnitudes 3 and 5-1/2, their colours orange and green. Perhaps there is
no more interesting double visible with low powers. The smaller star is
again double in first-class telescopes, the components being yellow and
blue according to some observers, but according to others, both green.

Below [gamma] Andromedæ lie the stars [beta] and [gamma] Triangulorum,
[gamma] a fine naked-eye triple (the companions being [delta] and [eta]