Aurora Spectra

PROCTER, HENRY R.

MR. CAPRON'S notice of my observations with regard to the auroral spectra compels me to say a few words with regard to them which I should rather have deferred till I could confirm my suspicions by fresh experiments. The spectrum which appears to coincide with the aurora, is not the ordinary spectrum of oxygen obtained by the disruptive discharge, but is, I have little doabt, that described by Wällner (Phil. Mag. p. 420, vol. xxxvii.) It is not uncommon in ordinary lumière tubes, but I obtained it with a feeble discharge in tubes filled with electrolytic oxygen, and therefore put it down to that gas. It is now two years since I made these experiments. Circumstances compelled me to leave the research incomplete, and I have hitherto been unable to return to it; but greater experience in the difficulties of spectrum work has suggested sources of error which I did not then suspect, and I should not feel any surprise if the spectrum in question turned out to be that of some carbon compound from the India rubber connections. It certainly has a strong family likeness to these, and if it were so, would confirm Prof. Piazzi Smyth's coincidence with citron acetylene. I will endeavour shortly to decide this.