+------+------------+------------------+ |Screw.|Wave-length.| Remarks. | +------+------------+------------------+ | 6·98 | 5603 |Very faint. | | 8·95 | 5189 |Very bright. | |11·26 | 4829 |Moderately bright.| +------+------------+------------------+ The lines near 3·97 and 11·02 belong to hydrogen. Probably traces of aqueous vapour were present in the tube, which were decomposed by the galvanic current. These two lines are not to be found in a lower temperature in the broad part of the tube. It is striking that the red nitrogen-line near 5·04 is also missing there. In the narrow part of the tube the lines stand out in the green on a very dimly-lighted ground, whilst in the wider part they appear on a perfectly dark ground. II. _Hydrogen._ _a._ In the narrow part of the tube. +------+------------+--------------------------------------------------+ |Screw.|Wave-length.| Remarks. | +------+------------+--------------------------------------------------+ | 3·98 | 6558 |Very bright. | | 6·16 | 5813 |Moderately bright, on both sides very faint lines.| | 7·01 | 5596 |Moderately bright.} On a dimly lighted ground, | | 7·18 | 5555 |Moderately bright.} which becomes fainter towards| | 7·77 | 5422 |Faint. } the violet. | | | | | | 8·95 | 5189 |Moderately bright.} | |10·03 | 5008 |Faint. } On a faint steadily bright | |10·55 | 4929 |Moderately bright.} ground. | | | | | |11·04 | 4861 |Very bright. } From 11·5 to 12·9 a bright | |12·86 | 4632 |Moderately bright.} ground, which towards the | | | | } violet becomes very bright. | | | | | |13·32 | 4581 |Very faint. } | |14·05 | 4506 | ” } On a dull ground. | |15·90 | 4342 |Very bright. } | +------+------------+--------------------------------------------------+ _b._ In the broad part of the tube. +-------+------------+------------------+ | Screw.|Wave-length.| Remarks. | +-------+------------+------------------+ | 5·30 | 6063 |Faint. | | 7·00 | 5598 |Bright. | | 8·96 | 5187 |Very bright. | | 11·28 | 4828 | ” | | 14·04 | 4507 |Moderately bright.| +-------+------------+------------------+ The lines appeared on a perfectly dark ground.