656 
MR. W. CROOKES OK MOLECULAR PHYSICS IK HIGH VACUA. 
618. I have long tried to obtain continuous rotation of the molecular rays under 
magnetic influence, analogous to the well known rotation obtained at lower exhaustions. 
Many circumstances had led me to think that such rotation could be effected. After 
many failures an apparatus was constructed as follows, which gave the desired results. 
A bulb (fig. 18) was blown of German glass, and a smaller bulb was connected to each 
end of the larger bulb by an open, very short neck. At each extremity was a long 
aluminium pole projecting partly into the large bulb and turned conical at the end. 
After good exhaustion the passage of an induction current through this apparatus 
fills the centre bulb with a very fine green light, whilst the neck surrounding the pole 
which happens to be negative is covered with two or three dark and bright patches in 
constant motion, following each other round first one way and then the other, constantly 
changing direction and velocity, sometimes dividing into other patches, and at others 
fusing together into one. After a little time, probably owing to the magnetism of 
the earth, or that of the core of the induction coil not far off, the movements sometimes 
become more regular, and slow rotation takes place. The patches of fight concentrate 
into two or three, and the green fight in the bulb gets more intense along two opposite 
fines joining the poles forming two faintly outlined patches, which slowly move round 
the bulb equatorially, following each other a semi-circumference apart. 
An electro-magnet placed beneath in a fine with the terminals (fig. 18), converts 
these undecided movements into one of orderly rotation, which keeps up as long as the 
coil and magnet are at work. 
619. In order to compare accurately the behaviour of the molecular streams at high 
exhaustions with that of the ordinary discharge through a moderately rarefied gas, 
