Supplementary table of wave-lengths of new lines in the secondary spectrum of hydrogen

During the course of the investigation of the secondary spectrum of hydrogen which is being carried out at King’s College, the present author had to take a number of spectrograms of a low potential and a low-pressure discharge of hydrogen known as the first-type discharge according to Prof. Richardson’s nomenclature. On measuring these first-type spectrum plates, it was found that each of them contained some eighty new lines not recorded in Merton and Barratt’s tables or in the table of additional lines recently published by Tanaka. At first it was suspected that these new lines might be due to some impurities in the discharge tube, but on carefully looking for impurities such as oxygen, nitrogen, carbon, mercury, barium, carbon monoxide, carbon dioxide, ammonia, water vapour, etc., it became evident that there were no impurity lines on our spectrum plates. It may be pointed out that before taking the first-type spectrogram of hydrogen, the discharge tube was being pumped out for a number of days, and it was then washed with hydrogen several times. The discharge tube was provided with a side tube containing coconut charcoal, which was surrounded by liquid air. This liquid-air trap was kept on during all exposures. Pure hydrogen was supplied by means of a palladium tube attached to the side of the discharge tube. This palladium tube was heated in a flame of commercial hydrogen.