128 Prof. Pliicker on the Action of the Magnet 



29. The same view is also supported, as far as we can judge 

 of the complex path of the magnetic lines of force, if in the first 

 series of experiments we make use of the heavy armatures. 



If, still keeping the tube equatorial, we bring the bulb con- 

 taining the warmth-pole above the place of greatest action, the 

 domelike-light surface appears with unusual distinctness. On 

 moving the tube, then, so as to keep it parallel with itself, towards 

 one or the other side, in an axial direction,, the surface alters its 

 form in a manner which may be previously determined from the 

 path of the magnetic curves existing at the time. 



30. We have now to describe those phEenomena which appear 

 when the tube through M'hich the discharge takes place is in an 

 xixial position (fig. 9). We shall, in the first place, again 

 employ the tube having bulbs at both ends, and place an 

 armature with conoidal point upon only one limb of the electro- 

 magnet. If, then, we so touch the tube, lying in an axial 

 position, that the warmth-electrode comes in contact with this 

 pole-point, the violet light streams into the tube, assuming the 

 form of a cylinder. The green light collects with especial 

 brilliancy at the entrance of the tube, from thence spreading 

 out over the inner surface of the bulb, and being sharply 

 bordered towards the centre of the bulb by a circle, the plane 

 of which is perpendicular to the axial direction, and which is 

 distant from the entrance of the tube about one-fourth of the 

 diameter of the bulb. 



On inversion, it appears as if both the violet and green light 

 first returned to the platinum electrode and then moved forwards 

 again, occupying finally exactly the same position as before. 

 During such motion the green light remains in the neighbour- 

 hood of the glass. 



31. The following series of experiments were performed with 

 a tube tapering conically towards one end. Its greatest dia- 

 meter at the wider end was 40 millims. At this end the 

 platinum wire intended for the warmth-electrode entered, pene- 

 trating to a distance of 23 millims. When the discharge 

 passed through the tube towards the platinum wire, the latter 

 was suiTOunded by the difirised light sharply bordered by the 

 dark space, which extended almost 60 milhnis. into the interior 

 of the tube. Beyond this dark space the dark bands appeared 

 extending through the whole tube, at first about 3 millims. 

 apart, but gradually approaching one another towards the end 

 of the tube. In the neighbourhood of the warmth-pole these 

 bands assumed the form of spherical surfaces, whose convex 

 sides wei'e tui'ned towards that pole. On inverting the current, 

 the direction of curvature of the stratified light was changed, 

 the layers reaching now to the platinum wire itself, which had 



