rpass him in
brilliancy and magnitude.

DOUBLE STARS.--To the unaided eye, these appear as single points of
light; but, when observed with a telescope of sufficient magnifying
power, their dual nature can be detected.

The first double star discovered was Mizar, the middle star of the three
in Ursa Major which form the tail of the bear. The components are of the
fourth and fifth magnitudes, of a brilliant white colour, and distant
fourteen seconds of arc.

In 1678, Cassini perceived stars which appeared as single points of
light when viewed with the naked eye, but when observed with the
telescope presented the appearance of being double.

The astronomer Bode, in 1781, published a list of eighty double stars,
and, in a few years after, Sir William Herschel discovered several
hundreds more of those objects. They are now known to exist in
thousands, Mr. Burnham, of the Lick Observatory, having, by his keen
perception of vision, contributed more than any other observer to swell
their number.

All double stars are not binaries; many of them are known as 'optical
doubles'--an impression created by two stars when almost in the same
line of vision, and, though apparently near, are situated at a great
distance apart and devoid of any physical relationship.

Binary stars consist of two suns which revolve round their common
centre of gravity, and form real dual systems.

The close proximity of the components of double stars impressed the
minds of some astronomers with the belief that a physical bond of union
existed between them. In the interval between 1718 and 1759, Bradley
detected a change of 30 deg. in the position angle of the two stars forming
Castor, and was very nearly discovering their physical connection.

In 1767, the Rev. John Michell wrote: 'It is highly probable in
particular, and next to a certainty in general, that such double stars
as appear to consist of two or more stars placed very near together do
really consist of stars placed near together and under the influence of
some general law.' Afterwards he says: 'It is not improbable that a few
years may inform us that some of the great number of double and triple
stars which have been observed by Mr. Herschel are systems of bodies
revolving about each other.' Christian Mayer, a German astronomer,
formed a list of stellar pairs, and announced, in 1776, the supposed
discovery of 'satellites' to many of the principal stars. His
observations were, however, n