proto-iron

Updated: July 23, 2026

But when the paper goes on to speak of the actual chemical nature of the sun-spots, as tested by a spectroscope; to tell of a "cool" stage when the vapor of iron furnishes chief spectrum lines, and of a "hot" stage when the iron has presumably been dissociated into unknown "proto-iron" constituents then indeed does it go far beyond the comprehension of the keenest eighteenth-century intellect, though keeping within the range of understanding of the mere scientific tyro of to-day.

Edward Huntington Williams - A History of Science, Volume 5 : Aspects Of Recent Science