‎ÅNGSTRÖM, (ANDERS JONAS). - HIS DOCTORAL DISSERTATION.‎
‎De Theoria Lucis Calorisque Dissertatio. (Pars I-II).‎

‎Uppsala, Regiae Academiae Typographi, 1839. Small 4to. Sewn as issued, uncut. (4),1-10,11-20 pp. Fine and clean. Printed on thick blue paper.‎

Reference : 45925

‎First edition of Ångströms scarce doctoral dissertation, dealing with the optics of conical refraction.Ångström was one of the early formulators of the science of modern spectroscopy he wrote extensively on terrestrial magnetism, the conduction of heat, and especially spectroscopy. He published a monumental map of the normal solar spectrum that expressed the length of light waves in units of one ten-millionth of a millimeter, a unit of length now known as the angstrom. He discovered that hydrogen is present in the sun's atmosphere, and he was the first to examine the spectrum of the aurora borealis.‎