MAGNETIC CHARACTER OF OXYGEN GAS. 
21 
with nitrogen gas, and then sealed them up hermetically. The end of the prolonged 
part of each was touched whilst warm with sealing-wax and a thread fastened to it, 
which thread was tied into a loop, also represented of full size. By these the tubes 
were to be suspended perpendicularly from a torsion balance, so that the middle of 
each should, when in place, be on a level with the magnetic axis. 
2773. The torsion balance consisted of a bundle of sixty equally stretched cocoon 
silk fibres, made fast above to a vertical axis carrying a horizontal index and gradu- 
ated plate, and below to a horizontal lever. A cross bar, about 1^ inch long, was 
attached to one end of this lever, also in the horizontal plane ; and on the extremities 
of this cross bar, and 8^ inches from the centre of motion, were hung the two tubes 
of oxygen and nitrogen (2772.), counterbalanced by a weight on the other arm of the 
horizontal level. The whole was thus so placed and adjusted in relation to the elec- 
tro-magnet, furnished at the time with the double cone core or keeper (2764.), that 
the middle part of each tube was level with the middle of the core, and equidistant 
on each side from it. Under these circumstances, if any motion was given to the 
balance, so as to make its arm vibrate, the vibrations were made with great slowness, 
in consequence of the weight of the whole moving arrangement, and the small amount 
of torsion force in the cocoon silk. 
2774. The moment the magnetic force was thrown into action all things changed. 
The oxygen tube was immediately carried inwards towards the axis, and the nitrogen 
tube driven outwards on the contrary side. The balance swung beyond its new place 
of rest and then returned with considerable power, vibrating many times in the 
period, which before was filled by a single oscillation ; and when it^had come to its 
place of rest, or of stable equilibrium, the oxygen tube was about one-eighth of an 
inch from the iron of the core, and the nitrogen tube four-eighths distant. Ten revo- 
lutions of the torsion axis altered only in a slight degree these relative distances. 
2775. The actions which determine the mutual self-adjustment of the oxygen and 
nitrogen, as regards their place in relation to the magnetic axis, are very simple and 
evident. In the first place, the glass of the tubes is more diamagnetic than the sur- 
rounding medium or air (2424.), and therefore each tends to move outwards ; but 
being equal in nature and condition to each other, they tend to move with equal force 
when at equal distances, and at those distances compensate each other. If one be 
driven inwards, it is subjected to a greater exertion of force by coming into a more 
intense part of the magnetic field ; and the other, being at the same time carried out- 
wards, is for a corresponding reason in a place of less intense action ; and therefore, as 
soon as the constraint is removed, the system returns to its position of stable equili- 
brium, in which the two bodies are equidistant from the magnetic axis. 
2776. The contents also of the tubes are subject to the magnetic forces, and as the 
result shows (2774.), in .very different degrees. Either the oxygen tends inwards 
much more forcibly than the nitrogen, or the nitrogen tends outwards more power- 
fully than the oxygen ; and the difference must exist to a very great degree, for it is 
such as to carry the glass of the oxygen tube up to a position so near the axis that it 
