cured of the true Milky Way, July 28,
August 1 and 2, 1889, at the Lick Observatory. Special conditions were
required for success; above all, a wide field and a strong light-grasp,
both complied with through the use of a 6-inch portrait-lens. Even thus,
the sensitive plate needed some hours to pick out the exceedingly faint
stars collected in the galactic clouds. These cannot be photographed
under the nebulous aspect they wear to the eye; the camera takes note of
their real nature, and registers their constituent stars rank by rank.
Hence the difficulty of disclosing them. "In the photographs made with
the 6-inch portrait-lens," Professor Barnard wrote, "besides myriads of
stars, there are shown, for the first time, the vast and wonderful
cloud-forms, with all their remarkable structure of lanes, holes, and
black gaps, and sprays of stars. They present to us these forms in all
their delicacy and beauty, as no eye or telescope can ever hope to see
them."[1622] In Plate VI. one of these strange galactic landscapes is
reproduced. It occurs in the Bow of Sagittarius, not far from the Trifid
nebula, where the aggregations of the Milky Way are more than usually
varied and characteristic. One of their distinctive features comes out
with particular prominence. It will be noticed that the bright mass near
the centre of the plate is tunnelled with dark holes and furrowed by
dusky lanes. Such interruptions recur perpetually in the Milky Way. They
are exemplified on the largest scale in the great rift dividing it into
two branches all the way from Cygnus to Crux; and they are reproduced in
miniature in many clusters.

PLATE VI.

[Illustration: Region of the Milky Way in Sagittarius--showing a double
black aperture.

Photographed by Professor E. E. Barnard.]

Mr. H. C. Russell, at Sydney in 1890, successfully imitated Professor
Barnard's example.[1623] His photographs of the southern Milky Way have
many points of interest. They show the great rift, black to the eye, yet
densely star-strewn to the perception of the chemical retina; while the
"Coal-sack" appears absolutely dark only in its northern portion. His
most remarkable discovery, however, was that of the spiral character of
the two Nubeculae. With an effective exposure of four and a half hours,
the Greater Cloud came out as "a complex spiral, with two centres";
while the similar conformation of its minor companion developed only
after eight hours of persistent actinic