The Light of the Night Sky

The two lines at 4416A and 4168A, recently reported by Lord Rayleigh in the light of a very bright night sky, are identified as ${\mathrm{O}}_{\mathrm{II}}$ lines. A theory is proposed which accounts for the strong excitation of the green aurora line both in the night sky and in the aurora borealis. The theory explains why no ${\mathrm{O}}_2$+ bands are found in the aurora while ${\mathrm{N}}_2$+ bands are very strong. Explanations are proposed for the two lines of singly-ionized oxygen and for the continuous spectrum in the night sky. Experiments performed by the writer substantiate the theory.