Two new lines have been observed in the spectrum of cuprous oxide (Cu 2O). The lines are very weak and situated in the spectrum at : λ 1 = 5 798 Å, λ2 = 5 829 Å. Some evidence has been obtained in favour of the interpretation of the λ1 line as a forbidden transition towards the exciton level 2S of the yellow series. It is suggested that the λ2 line corresponds to a forbidden transition towards the state n = 1 of the green series.Nous avons observé deux raies faibles nouvelles dans le spectre de Cu 2O : λ1 = 5 798 Å, λ2 = 5 829 Å. Diverses expériences et considérations nous conduisent à suggérer que la raie λ 1 correspond à une transition défendue vers l'état 2S de la série jaune, la raie λ2 pourrait être une transition vers l'état n = 1 de...