232 NOTICES OF THE MEETINGS [Jan. 21, 
glass cylinder weighing only 66 grains surrounded by air was sub- 
mitted on the torsion balance to the Logeman magnet at the distance 
of 0.5 of an inch from the axial line, it required 15° of torsion to 
overcome the repulsive force and restore the object to its place. 
When a vessel of water was put into the magnetic field, and the 
experiment repeated, the cylinder being now in the water was 
attracted, and 54°.5 of torsion were required to overcome this attrac- 
tion at the given distance of 0.5. If the vessel had contained a 
fluid exactly equal in diamagnetic power to the cylinder of glass, 
neither attraction nor repulsion would have been exerted on the 
latter, and therefore the torsion would have been 0°. Hence the 
three bodies, air, glass (the especial specimen), and water, have their 
relative force measured in relation to each other by the three ex- 
perimental numbers 15°, 0°, and 54°5. If other fluids are taken, 
as oil, ether, &c. and employed as the media surrounding the same 
glass cylinder, then the degrees of torsion obtained with each of 
them respectively, shews its place in the magnetic series. It is the 
principle of the hydrometer or of Archimedes in respect of gravity 
applied in the case of the magnetic forces. Ifa different cylinder be 
employed of another size or substance, or at a different distance, 
the torsion numbers will be different, and the zero (given by the 
cylinder) also different ; but the media (with an exception to be 
made hereafter) will have the same relation to each other as in 
the former case. Therefore to bring all the experimental results 
into one common relation, a centigrade scale has been adopted 
bounded by air and water at common temperatures or 60° F. 
For this purpose every separate series of results made under exactly 
the same circumstances included air and water; and then all the 
results of one series were multiplied by such a number as would 
convert the difference between air and water into 100°: in this way 
the three results given above, become 21°.6; 0°; and 78°.4. By 
such a process the magnetic intervals between the bodies are ob- 
tained on the centigrade scale, but the true zero is not as yet de- 
termined. Either water, or air, or the glass, may be assumed as the 
zero, the intervals not being in any way dependent upon that point, 
but the results will then vary in expression thus :— 
Air : 0° i D126 Y 100° 
Glass .  21°.6 _ (ae é 78°.4 
Water . 100° : 78°.4 : 0° 
all above the zero being paramagnetic, and all below diamagnetic, 
in relation to it. I have adopted a vacuum as the zero in the table 
of results to be given hereafter. 
In this manner it is evident that upon principle, any solid, what- 
ever its size, shape, or quality, may be included in the list, by its 
subjection to a magnet in air and in water or in fluids already 
related to these: also that any fluids may be included by the use 
of the same immersed solid body for them, air and water; and also 
that by using the same vessel, as for instance the same glass bulb, 
