, as
clouds choke a mountain valley. The chief points of its
concentration are the four stars Alcyone, Merope, Maia, and
Electra; but it includes as well Celoeno and Taygeta, and is
traceable southward from Asterope over an arc of 1 deg. 10'. . . .
The greater part of the constellation is shown as veiled in
nebulous matter of most unequal densities. In some places it
lies in heavy folds and wreaths, in others it barely qualifies
the darkness of the sky-ground. The details of its
distribution come out with remarkable clearness, and are
evidently to a large extent prescribed by the relative
situations of the stars. Their lines of junction are
frequently marked by nebulous rays, establishing between them,
no doubt, relations of great physical importance; and masses
of nebula, in numerous instances, seem as if _pulled out of
shape_ and drawn into festoons by the attractions of
neighbouring stars. But the strangest exemplification of
this filamentous tendency is in a fine, thread-like process,
3'' or 4'' wide, but 35' to 40' long, issuing in an easterly
direction from the edge of the nebula about Maia, and
stringing together seven stars, met in its advance, like beads
on a rosary. The largest of these is apparently the occasion
of a slight deviation from its otherwise rectilinear course. A
second similar but shorter streak runs, likewise east and
west, through the midst of the formation."[229:1]

[Illustration: NEBULOSITIES OF THE PLEIADES.

Photographed by Dr. Max Wolf, Heidelberg.]

Later photographs have shown that not only are the several stars of the
Pleiades linked together by nebulous filaments, but the whole cluster is
embedded in a nebulous net that spreads its meshes far out into space.
Not only is the group thus tied or bound together by nebulous clouds, it
has other tokens of forming but a single family. The movements of the
several stars have been carefully measured, and for the most part the
entire cluster is drifting in the same direction; a few stars do not
share in the common motion, and are probably apparent members, seen in
perspective projected on the group, but in reality much nearer to us.
The members of the group also show a family likeness in constitution.
When the spectroscope is turned upon it, the chief stars are seen to
closely resemble each other; the principal lines in thei