MR. W. CROOKES ON MOLECULAR PHYSICS IN HIGH VACUA. 
653 
shifted its position up to d g. The same phenomena were observed when the pole b 
was connected with the coil, and contact was alternately made and broken with a ; as 
the ray d g shot across, the ray e f dipped to e h. 
These experiments show that two parallel rays of molecules issuing from the nega¬ 
tive pole exert lateral repulsion, acting like adjacent streams of similarly-electrified 
bodies. Had they carried an electric current they should have attracted each other, 
unless, indeed, the attraction in this case was not strong enough to overcome the 
repulsion. 
611. Many experiments have been made to ascertain the law of the action of 
magnets and of wires carrying currents, on the stream of molecules. 
As an indicator, a small tube, as shown in fig. 14, was employed. The two poles 
are at a and b, a being the negative. At c is a plate of mica with a hole in its centre, 
and at d is a phosphorescent screen. A sharp image of the hole in the mica is pro¬ 
jected on the centre of d, and the approach of a magnet causes this bright spot to 
move to different parts of the phosphorescent screen. 
Fig. 14. 
A large electro-magnet was used, actuated by two Grove’s cells, and the indicator 
tube was carried round the magnet in different positions and the results noted. 
The molecular stream when under no magnetic influence passes along the axis of the 
tube, as shown by the small arrow (fig. 14). It will be seen that the indicator can 
occupy three different directions in respect to the magnet. The magnet being held 
horizontally, the direction of the molecular stream maybe parallel to the axis, tangen¬ 
tial to it, or at right angles to it. In either of these positions, also, the stream may 
be directed one way or the other (by turning the tube round endwise). In these 
different positions various results are obtained which are easily illustrated with a solid 
model, but are somewhat complicated to explain by means of flat drawings. In figs. 
15, 16, and 17 I have separated the effects one from the other, and I hope with the 
accompanying description that they will be intelligible. 
612. Fig. 15 shows the electro-magnet lying horizontally, the current passing in 
such a direction that the S pole is on the left. The indicator tube is supposed to be 
held in front of the magnet and at right angles to its axis, the stream of molecules 
moving, when not under magnetic influence, vertically up or down according as the 
negative electrode is at the bottom or the top. The black arrows represent the diffe¬ 
rent positions in which the indicator tube was held, and the direction of the arrow 
shows the direction of the molecular stream. The point of the arrow would fall on the 
phosphorescent screen, and the feather end represents the hole in the mica plate. 
