ked it until about 1826, when Louis J. M.
Daguerre, the French chemist, took the matter in hand, and after many
years of experimentation brought it to relative perfection in 1839, in
which year the famous daguerreotype first brought the matter to popular
attention. In the same year Mr. Fox Talbot read a paper on the subject
before the Royal Society, and soon afterwards the efforts of Herschel
and numerous other natural philosophers contributed to the advancement
of the new method.

In 1843 Dr. John W. Draper, the famous English-American chemist and
physiologist, showed that by photography the Fraunhofer lines in the
solar spectrum might be mapped with absolute accuracy; also proving that
the silvered film revealed many lines invisible to the unaided eye. The
value of this method of observation was recognized at once, and, as
soon as the spectroscope was perfected, the photographic method, in
conjunction with its use, became invaluable to the chemist. By this
means comparisons of spectra may be made with a degree of accuracy
not otherwise obtainable; and, in case of the stars, whole clusters of
spectra may be placed on record at a single observation.

As the examination of the sun and stars proceeded, chemists were amazed
or delighted, according to their various preconceptions, to witness the
proof that many familiar terrestrial elements are to be found in the
celestial bodies. But what perhaps surprised them most was to observe
the enormous preponderance in the sidereal bodies of the element
hydrogen. Not only are there vast quantities of this element in the
sun's atmosphere, but some other suns appeared to show hydrogen lines
almost exclusively in their spectra. Presently it appeared that the
stars of which this is true are those white stars, such as Sirius, which
had been conjectured to be the hottest; whereas stars that are only
red-hot, like our sun, show also the vapors of many other elements,
including iron and other metals.

In 1878 Professor J. Norman Lockyer, in a paper before the Royal
Society, called attention to the possible significance of this series of
observations. He urged that the fact of the sun showing fewer elements
than are observed here on the cool earth, while stars much hotter than
the sun show chiefly one element, and that one hydrogen, the lightest of
known elements, seemed to give color to the possibility that our alleged
elements are really compounds, which at the temperature of the hottes