The further extension of the ultra-violet spectrum and the progression with atomic number of the spectra of light elements

The chief purpose of this investigation, outlined and begun in 1916(1) and briefly reported upon last year,(2) has been to explore in the extreme ultra-violet the radiations which can be emitted by the second ring or shell of electrons in the atoms of atomic number from 2 to 13 (helium to aluminium).(3)