Question

In the late 1860s, solar spectroscopic studies by Norman Lockyer and Jules Janssen revealed an unidentified bright yellow emission line in the solar chromosphere spectrum, which Lockyer hypothesized belonged to an element unknown on Earth, named helium. For nearly three decades, mainstream terrestrial chemists remained skeptical of Lockyer's claim, viewing spectral anomalies as mere artifacts of high solar temperatures or pressure-induced line broadening in known elements like hydrogen. This skepticism reflected a broader methodological commitment within nineteenth-century chemistry to elemental isolation: a substance could not be formally cataloged as a distinct chemical element without laboratory isolation and macroscopic atomic weight determination. Consequently, when William Ramsay isolated helium in 1895 from the uranium-bearing mineral cleveite, the discovery did not merely confirm Lockyer's astronomical inference; it fundamentally challenged the epistemological hierarchy that privileged terrestrial laboratory synthesis over celestial observational physics. Ramsay's achievement forced chemists to accept spectroscopic signatures as sufficient evidence for elemental existence, thereby accelerating the integration of astrophysics into standard chemical taxonomy.

Based on the passage, which of the following can be inferred regarding nineteenth-century terrestrial chemists prior to Ramsay's 1895 discovery? Consider each of the choices separately and select all that apply.