ed upon
the development of its nebulous proclivities; and its surviving rays are
of a steely hue.

All the more important investigations of Nova Persei were conducted by
photographic means. Libraries of spectral plates were collected at the
Yerkes and Lick Observatories, at South Kensington, Stonyhurst, and
Potsdam, and await the more exhaustive interpretation of the future.
Meanwhile, extraordinary revelations have been supplied by immediate
photographic delineation. On August 22 and 23, 1901, Professor Max Wolf,
by long exposures with the 16-inch Bruce twin objectives of the
Koenigstuhl Observatory (Heidelberg), obtained indications of a large
nebula finely ramified, extending south-east of the Nova;[1505] and the
entire formation came out in four hours with the Yerkes 2-foot
reflector, directed to it by Mr. Ritchey on September 20.[1506] It
proved to be a great spiral encircling, and apparently emanating from,
the star. But if so, tumultuously, and under stress of catastrophic
impulsions. A picture obtained by Mr. Perrine with the Crossley
refractor, in 7h. 19m., on November 7 and 8, disclosed the progress of a
startling change.[1507] Comparison with the Yerkes photograph showed
that during the intervening 48 days four clearly identifiable
condensations had become displaced, all to the same extent of about 90
seconds of arc, and in fairly concordant directions, suggesting motion
_round_ the Nova as well as away from it. The velocity implied, however,
is so prodigious as virtually to exclude the supposition of a bodily
transport of matter. It should be at the rate of no less than twenty
thousand miles a second, admitting the object to be at a distance from
us corresponding to an annual parallax of one-tenth of a second, and
actual measurements show it to be indefinitely more remote. The fact of
rapid variations in the nebula was reaffirmed, though with less
precision, from Yerkes photographs of November 9 and 13, Mr. Ritchey
inferring a general expansion of its southern portions.[1508] Much
further evidence must be at hand before a sane judgment can be formed as
to the nature of the strange events taking place in that secluded corner
of the Galaxy.[1509] And it is highly probable that the illumination of
the nebulous wreaths round the star will prove no less evanescent than
the blazing of the star itself.

We have been compelled somewhat to anticipate our narrative as regards
inquiries into the nature of nebulae. Th