  In 1896, Edward Charles Pickering (1846-1919), Director of the Harvard
College Observatory (HCO), reported in a trio of publications the observation
of "peculiar spectra" of the southern star $\zeta$ Puppis, which he attributed
to an "element not yet found in other stars or on earth." Supported by
laboratory spectra obtained by Alfred Fowler (1868-1940), Niels Bohr
(1885-1962) showed in 1913 that this "element" was in fact ionized helium,
He$^+$. Its spectrum has become known as the Pickering Series, even though
Pickering credited Williamina Fleming (1857-1911) for the discovery. Fleming
was one of HCO's "computers" and the future Curator of the Astronomical
Photographic Glass Plate Collection. The series of spectral lines associated
with Pickering's name played a unique role on the path to quantum mechanics by
serving as a proving ground for Bohr's model of the atom. Our examination of
the discovery of the Pickering series relied on the records held at the Center
for Astrophysics $\vert$ Harvard \& Smithsonian (the successor institution to
HCO), especially the Notebooks and Diaries of Williamina Fleming and others as
well as on the Center's Glass Plate Collection. Glimpses of the "peculiar
sociology" of a research institution, half of whose staff were women employed
on grossly unequal terms with men, are given in the course of the narrative.
