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point of view of the importance of finding
out the divergence of a cometary orbit from
a parabola, its period, and its aphelion dis-
tance, this increase of range attains the very
highest value.
The present Astronomer Royal, appreci-
ating this possibility, has been searching by
photography for Halley’s comet since Novem-
ber, 1907, although its perihelion passage
568