I. The Widening of Iron Lines and of Unknown Lines in Relation to the Sun-spot Period. IT is now twenty-eight years since I discovered that the lines seen in sun-spots were subject to widening,2 and that different lines were widened at different times.
A Paper read at the Royal Society, by J. Norman Lockyerv C.B., F.R.S.
"Roy. Soc. Proc." vol. xv. p. 256, 1866.
"Roy. Soc. Proc." vol. xl. p. 347.
"Roy. Soc. Proc." vol. liv. p. 359.