and significant; it could
not result merely from the casually directed, opposite velocities of
bodies meeting in space. The hypothesis of stellar encounters
accordingly fell to the ground, and has been provided with no entire
satisfactory substitute. Most speculators now fully recognise that
motion-displacements cannot be made to account for the doubled spectra
of Novae, and seek recourse instead to some kind of physical agency for
producing the observed effect.[1501] And since this is also visible in
certain permanent, though peculiar objects--notably in P Cygni,
Beta Lyrae, and Eta Carinae--the acting cause must also evidently be
permanent and inherent.

The "new star of the new century"[1502] was a visual discovery. Dr.
Anderson duplicated, with added _eclat_, his performance of nine years
back. In the early morning of February 22, 1901, he perceived that Algol
had a neighbour of nearly its own brightness, which a photograph taken
by Mr. Stanley Williams, at Brighton, proved to have risen from below
the twelfth magnitude within the preceding 28 hours. And it was still
swiftly ascending. On the 23rd, it outshone Capella; for a brief space
it took rank as the premier star of the northern hemisphere. A decline
set in promptly, but was pursued hesitatingly. The light fluctuated
continually over a range of a couple of magnitudes, and with a close
approach, during some weeks, to a three-day periodicity. A year after
the original outburst, the star was still conspicuous with an
opera-glass. The spectrum underwent amazing changes. At first
continuous, save for fine dark lines of hydrogen and helium, it unfolded
within forty-eight hours a composite range of brilliant and dusky bands
disposed in the usual fashion of Novae. These lasted until far on in
March, when hydrogen certainly, and probably other substances as well,
ceased to exert any appreciable absorptive action. Blue emissions of the
Wolf-Rayet type then became occasionally prominent, in remarkable
correspondence with the varying lustre of the star;[1503] finally, a
band at Lambda 3969, found by Wright at Lick to characterise nebular
spectra,[1504] assumed abnormal importance; and in July the nebular
transformation might be said to be complete. Striking alterations of
colour attended these spectral vicissitudes. White to begin with, the
star soon turned deep red, and its redness was visibly intensified at
each of its recurring minima of light. Blanching, however, ensu