Page 424 - 89 history of astronomy_opt

Another method of obtaining spectra had
long been known, by transmission through,
or reflection from, a grating of equidistant
lines ruled upon glass or metal. H. A. Row-
land developed the art of constructing these
gratings, which requires great technical skill,
and for this astronomers owe him a debt of
gratitude.
In 1842 Doppler[5] proved that the colour
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