Page 473 - 89 history of astronomy_opt

of Baltimore, after having perfected the art
of making true gratings with equidistant
lines ruled on metal for producing spectra,
then proceeded to make a map of the solar
spectrum on a large scale.
In 1866 Lockyer[9] threw an image of the
sun upon the slit of a spectroscope, and was
thus enabled to compare the spectrum of a
spot with that of the general solar surface.
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