1853.] OF THE ROYAL INSTITUTION. 235 
in tenths of an inch from the axial line of the magnetic field, 
and the second, the place in centigrade magnetic degrees below water. 
Flint Glass. Heavy Glass. Bismuth. 
0.3 — 91 0.38 — 37°8 0.6 — 1871° 
0.4 — 10.6 0.4 — 38.6 1.0 — 2734. 
0.5 — 11.1 0.6 — 40.0 1.5 — 3626. 
0.6 — 11.2 0.8 — 48.6 
0.7 — 12.1 1.0 — 51.5 
1.2 — 65.6 
The result here is that the greater the distance of the diamag- 
netic bodies from the magnet, the more diamagnetic is it in relation 
- to water, taking the interval between water and air as the standard : 
and it would further appear, if an opinion may be formed from so few 
experiments, that the more diamagnetic the body compared to air 
and water, the greater does this difference become. At first it was 
thought possible that the results might be due to some previous 
state induced upon the body, by its having been nearer to or further 
from the magnet: but it was found that whether the progress of 
the experiments was from small to large distances, or the reverse ; 
or whether, at any given distance, the object was previous to the 
measurement held close up to the magnet or brought from a 
distance, the results were the same ;— no evidence of a temporary 
induced state could in any of these ways be found. 
It does not follow from the experiments, if they should be 
sustained by future researches, that it is the glass or the bismuth 
only that changes in relation to the other two bodies. It may be 
the oxygen of the air that alters, or the water, or more probably 
all these bodies: for if the result be a true and natural result in 
these cases, it is probably common to all substances. The great 
-point is that the three bodies concerned, air, water, and the subject 
of the experiment, alter in the degree of their magnetic relations 
to each other; at different given distances from the magnet the 
ratio of their magnetic power does not, according to the experi- 
ments, remain the same; and if that result be confirmed, then 
it cannot be included by a law of action which is inversely as the 
square of the distance. A hydrometer floating in a fluid and 
subject to the gravity of the earth alone, would (other things being 
the same) stand at the same point, whether at the surface of the 
earth, or removed many diameters of the earth from it, because the 
action of gravity is inversely as the square of the distance: but if 
we suppose the substance of the hydrometer and the fluid to differ 
magnetically, as water and bismuth does, and the earth to act as a 
magnet instead of by gravity, then the hydrometer . would, 
according to the experiments, stand at a different point for different 
distances, and if so could not be subject to the former law. 
is not in the same proportion. By fitly arranged terminations, it may be made 
to alter with extreme rapidity in one direction, and with extreme slowness or 
not at all in another. 
