234 NOTICES OF THE MEETINGS [Jan. 21, 
action may be divided into two kinds, that between magnets 
permanently magnetized and unchangeable in their condition, 
and that between bodies of which one is a permanent un- 
changeable magnet, and the other, having no magnetic state 
of its own, receives and retains its state only whilst in subjection to 
the first. The former kind of action appears in the most rigid and 
pure cases, to be subject to that law; but it would be premature 
to assume beforehand, and without abundant sufficient evidence, that 
the same law applies in the second set of cases also; for a hasty 
assumption might be in opposition to the truth of nature, and 
therefore injurious to the progress of science, by the creation of a 
preconceived conclusion. We know not whether such bodies as 
oxygen, copper, water, bismuth, &c., owe their respective para- 
magnetic and diamagnetic relation to a greater or less facility of 
conduction in regard to the lines of magnetic force, or to something 
like a polarity of their particles or masses, or to some as yet 
unsuspected state; and there is little hope of our developing the 
true condition, and therefore the cause of magnetic action, if we 
assume beforehand the unproved law of action and reject the 
experiments that already bear upon it :— for Pliicker has distinctly 
stated as the fact, that diamagnetic force increases more rapidly 
than magnetic force, when the power of the dominant magnet is 
increased ; and such a fact is contrary to the law above enunciated. 
The following are further results in relation to this point. 
When a body is submitted to the great unchanging Logeman 
magnet in air and in water, and the results are reduced to the 
centigrade scale, the relation of the three substances remain the 
same for the same distance, but not for different distances. Thus 
when a given cylinder of flint glass was submitted to the magnet 
surrounded by air and by water, at the distance of 0.3 of an inch as 
already described, it proved to be diamagnetic in relation to both ; 
and when the results were corrected to the centigrade scale, and 
water made zero, it was 9°.1 below, or on the diamagnetic side of 
water. At the distance 0.4 of an inch it was 10°.6 below water: 
at the distance of 0.7 it was 12°.1 below water. When a more 
diamagnetic body, as heavy glass, was employed, the same result 
in a higher degree was obtained ; for at the distance of 0.3 it was 
37°.8 below water, and at that of 0.8 it was 48°.6 beneath it. 
Bismuth presented a still more striking case, though, as the volume 
of the substance was necessarily small, equal confidence cannot be 
placed in the exactitude of the numbers. The results are given 
below for the three substances, air being always 100° and water 0° ; 
the first column of figures for each substance contain the distance * 
* A given change of distance necessarily implies change in degree of force, 
and change in the forms of the lines of force; but it does not imply always 
the same amount of change. The forces are not the same at the same dis- 
tance of 0.4 of an inch in opposite directions from the axial line towards mand 
n in the figure, page 230, nor at any other equal moderate distance; and though 
by increase and diminution of distance the change is in the same direction, it 
