the edge of the nebula is approached. In fact,
we can hardly say that the nebula has any definite boundary, for with
each increase of telescopic power faint new branches can be seen. There
seems to be an empty space in the nebula immediately surrounding the
multiple star, but this is merely an illusion, produced by the contrast
of the brilliant light of the stars, as the spectroscopic examination of
the nebula shows that the nebulous matter is continuous between the
stars.

The plate of the great nebula in Orion which is here shown (Plate XIV.)
represents, in a reduced form, the elaborate drawing of this object,
which has been made with the Earl of Rosse's great reflecting telescope
at Parsonstown.[40] A telescopic view of the nebula shows two hundred
stars or more, scattered over its surface. It is not necessary to
suppose that these stars are immersed in the substance of the nebula as
the multiple star appears to be; they may be either in front of it, or,
less probably, behind it, so as to be projected on the same part of the
sky.

[Illustration: PLATE XV.

PHOTOGRAPH OF THE NEBULA 31 M ANDROMEDAE

EXPOSURE 4 HOURS, ENLARGED 3 TIMES.

TAKEN BY MR. ISAAC ROBERTS, 29 DECEMBER, 1882.]

A considerable number of drawings of this unique object have been made
by other astronomers. Among these we must mention that executed by
Professor Bond, in Cambridge, Mass., which possesses a faithfulness in
detail that every student of this object is bound to acknowledge. Of
late years also successful attempts have been made to photograph the
great nebula. The late Professor Draper was fortunate enough to obtain
some admirable photographs. In England Mr. Common was the first to take
most excellent photographs of the nebula, and superb photographs of the
same object have also been obtained by Dr. Roberts and Mr. W.E. Wilson,
which show a vast extension of the nebula into regions which it was not
previously known to occupy.

The great nebula in Andromeda, which is faintly visible to the unaided
eye, is shown in Plate XV., which has been copied with permission from
one of the astonishing photographs that Dr. Isaac Roberts has obtained.
Two dark channels in the nebula cannot fail to be noticed, and the
number of faint stars scattered over its surface is also a point to
which attention may be drawn. To find this object we must look out for
Cassiopeia and the Great Square of Pegasus, and then the nebula will be
easily perceived in th