ACTION OF MAGNETS ON AIR AND GASES. 
51 
or their repulsions and attractions, might depend upon converse actions of the media 
by which they were surrounded (2361.), so I proceeded to examine what would occur 
with diamagnetic substances, when the air or gas which surrounded them was changed 
in its density or nature, or what would happen to air itself when surrounded by these 
substances. 
2406. The air-tube (2401.) was suspended horizontally in water (being retained 
below the surface by a cube of bismuth attached to it, just beneath the point of sus- 
pension, which therefore could have no power of giving it direction) ; it was then 
subjected to the magnetic forces, and immediately pointed well in an axial direction, 
or as a magnet would have done. Being brought near to one pole it moved, on the 
supervention of the magnetic force, appearing as if attracted after the manner of a 
magnetic body ; and this continued as long as the magnetic force was sustained in 
action. 
2407- The air-tube was in like manner subjected to the action of the magnetic 
force, when surrounded by alcohol, and also by oil of turpentine, with precisely the 
same results as in water. In all these cases the action of air in the fluids was pre- 
cisely the same as the action of a magnetic body in air. The air-tube was subjected 
to the action of the magnet even when under the surface of mercury, and here also 
it pointed axially. 
2408. In order to extend the experimental relations of air and gases, I proceeded 
to place substances of the diamagnetic class in them. Thus, the bar of heavy glass 
(2253.) was suspended in a jar of air, and then the air about it more or less rarefied, 
but, as before, in the case of the air-tube (2402.), alterations of this kind produced 
no effect. Whether the bar were in air at the ordinary pressure, or as rare as the 
pump could render it, it still pointed equatorially, and apparently always with the 
same degree of force. 
2409. The bar of bismuth (2296.) was suspended in the jar, and the same altera- 
tion in the density of the air made as before ; but this caused no difference in the 
action of the bismuth, either in kind or degree. Carbonic acid and hydrogen gases 
were then introduced in succession into the jar, and these also were employed in 
different degrees of rarefaction, but the results were the same ; no change took place 
in the action on the bismuth. 
2410. A bismuth cube was suspended in air and gases at ordinary pressure, and 
also rarefied as much as could be, and under these circumstances it was brought near 
the magnetic pole and its repulsion observed ; its action was in all these cases pre- 
cisely the same as in the atmosphere. 
2411. The perpendicular copper bar (2323.) was suspended near the magnetic pole 
in vacuo , but its set, sluggish movements and revulsion, were just the same as before 
in air (2324.). 
2412. The following preparations in tubes (2401.), namely, a vacuum, air, hydro- 
gen, carbonic acid gas, sulphurous acid gas, and vapour of ether, were surrounded 
h 2 
