many more.

When Halley's comet reappeared in 1835, Pontecoulant's computations
for the date of perihelion passage were very exact, and afterwards he
showed that, with more exact values of the masses of Jupiter and
Saturn, his prediction was correct within two days, after an invisible
voyage of seventy-five years!

Hind afterwards searched out many old appearances of this comet, going
back to 11 B.C., and most of these have been identified as being
really Halley's comet by the calculations of Cowell and Cromellin[4]
(of Greenwich Observatory), who have also predicted its next
perihelion passage for April 8th to 16th, 1910, and have traced back
its history still farther, to 240 B.C.

Already, in November, 1907, the Astronomer Royal was trying to catch
it by the aid of photography.


FOOTNOTES:

[1] Born 1736; died 1813.

[2] Born 1749; died 1827.

[3] This sentence does not appear in the original memoir communicated
to the Royal Society, but was first published in a posthumous reprint.

[4] _R. A. S. Monthly Notices_, 1907-8.