mfortably
early morning hours, and I can well remember myself feeling rather more
resentment than gratitude to the man who waked me up about four o'clock to
see it. Many observations were of course made of this interesting visitor,
and what specially concerns us is that at the Cape of Good Hope some
enterprising photographers tried to photograph it. They tried in the first
instance with ordinary cameras, and soon found--what any astronomer could
have told them--that the movement of the earth, causing an apparent
movement of the comet and the stars in the opposite direction, frustrated
their efforts. The difficulties of obtaining pictures of moving objects
are familiar to all photographers. A "snap-shot" might have met the
difficulty, but the comet was scarcely bright enough to affect the plate
with a short exposure. Ultimately Dr. David Gill, the astronomer at the
Cape Observatory, invited one of the photographers to strap his camera to
one of the telescopes at the Observatory, a telescope which could be
carried round by clockwork in the usual way, so as to counteract the
earth's motion, and in effect to keep the comet steadily in view, as
though it were at rest. As a consequence, some very beautiful and
successful pictures of the comet were obtained, and on them a large number
of stars were also shown. They were, as I have said, not by any means the
first pictures of stars obtained by photography, but they represented in
facility and in success so great an advance upon what had been formerly
obtained that they attracted considerable attention. They were sent to
Europe and stimulated various workers to further experiments.

[Sidenote: The brothers Henry begin work.]

[Sidenote: Conference of 1887.]

The late Dr. Common in England, an amateur astronomer, began that
magnificent pioneer work in astronomical photography which soon brought
him the Gold Medal of the Royal Astronomical Society for his photographs
of nebulae. But the most important result for our purpose was produced in
France. There had been started many years before by the French astronomer
Chacornac a series of star maps round the Zodiac similar in intention to
the Berlin maps which figured in the history of the discovery of Neptune.
Chacornac died before his enterprise was very far advanced, and the work
was taken up by two brothers, Paul and Prosper Henry, who followed
Chacornac in adopting for the work the laborious method of eye
observation of each ind