stars hope to conceal when questioned by an instrument
of such necromantic power?

But the spectroscope is not alone in this audacious
assault upon the strongholds of nature. It has a worthy
companion and assistant in the photographic film,
whose efficient aid has been invoked by the astronomer
even more recently. Pioneer work in celestial
photography was, indeed, done by Arago in France and
by the elder Draper in America in 1839, but the results
then achieved were only tentative, and it was not till
forty years later that the method assumed really important
proportions. In 1880, Dr. Henry Draper, at
Hastings-on-the-Hudson, made the first successful
photograph of a nebula. Soon after, Dr. David Gill,
at the Cape observatory, made fine photographs of a
comet, and the flecks of starlight on his plates first
suggested the possibilities of this method in charting
the heavens.

Since then star-charting with the film has come virtually
to supersede the old method. A concerted effort
is being made by astronomers in various parts of the
world to make a complete chart of the heavens, and
before the close of our century this work will be accomplished,
some fifty or sixty millions of visible stars being
placed on record with a degree of accuracy hitherto
unapproachable. Moreover, other millions of stars
are brought to light by the negative, which are too distant
or dim to be visible with any telescopic powers