nother, but
that they have been originally fashioned, or have been built up, from
one another, according to some general plan." It is but a short step
from that proposition to the Proutian hypothesis.

NEW WEAPONS--SPECTROSCOPE AND CAMERA

But the atomic weights are not alone in suggesting the compound nature
of the alleged elements. Evidence of a totally different kind has
contributed to the same end, from a source that could hardly have been
imagined when the Proutian hypothesis, was formulated, through the
tradition of a novel weapon to the armamentarium of the chemist--the
spectroscope. The perfection of this instrument, in the hands of two
German scientists, Gustav Robert Kirchhoff and Robert Wilhelm Bunsen,
came about through the investigation, towards the middle of the century,
of the meaning of the dark lines which had been observed in the solar
spectrum by Fraunhofer as early as 1815, and by Wollaston a decade
earlier. It was suspected by Stokes and by Fox Talbot in England, but
first brought to demonstration by Kirchhoff and Bunsen, that these
lines, which were known to occupy definite positions in the spectrum,
are really indicative of particular elementary substances. By means of
the spectroscope, which is essentially a magnifying lens attached to a
prism of glass, it is possible to locate the lines with great accuracy,
and it was soon shown that here was a new means of chemical analysis
of the most exquisite delicacy. It was found, for example, that the
spectroscope could detect the presence of a quantity of sodium so
infinitesimal as the one two-hundred-thousandth of a grain. But what was
even more important, the spectroscope put no limit upon the distance of
location of the substance it tested, provided only that sufficient light
came from it. The experiments it recorded might be performed in the sun,
or in the most distant stars or nebulae; indeed, one of the earliest
feats of the instrument was to wrench from the sun the secret of his
chemical constitution.

To render the utility of the spectroscope complete, however, it
was necessary to link with it another new chemical agency--namely,
photography. This now familiar process is based on the property of light
to decompose certain unstable compounds of silver, and thus alter their
chemical composition. Davy and Wedgwood barely escaped the discovery of
the value of the photographic method early in the nineteenth century.
Their successors quite overloo