CONSIDERATIONS OF TERRESTRIAL DIAMAGNETIC ACTION. 
Gl 
former, and the mixture was neither attracted nor repelled. To produce this effect, 
it required that more than 48‘6 grains of crystallized protosulphate of iron should 
be added to ten cubic inches of water (for these proportions gave a solution which 
still set equatorially), a quantity so large, that I was greatly astonished on observing 
the power of the water to overcome it. It is not therefore at all unlikely that many 
of the masses which form the crust of this our globe may have an excess of diamag- 
netic power and act accordingly. 
2449. Though the general disposition of the magnetic curves which permeate and 
surround our globe resemble those of a very short magnet, and therefore give lines 
of force rapidly diverging in their general form, yet the magnitude of the system 
prevents us from observing any diminution of their power within small limits ; so 
that probably any attempt on the surface of the earth to observe the tendency of 
matter to pass from stronger to weaker places of action would fail. Theoretically, 
however, and at first sight, I think a pound of bismuth or of water, estimated at the 
equator, where the magnetic needle does not dip, ought to weigh less when taken 
into latitudes where the dip is considerable ; whilst a pound of iron, nickel, or cobalt, 
ought, under the same change of circumstances, to weigh more. If such should 
really prove to be the case, then a ball of iron and another of bismuth, attached to 
the ends of a delicate balance beam, should cause that beam to take different incli- 
nations on different parts of the surface of the earth ; and it does not seem quite 
impossible that an instrument to measure one of the conditions of terrestrial mag- 
netic force might be constructed on such a principle. 
2450. If one might speculate upon the effect of the whole system of curves upon 
very large masses, and these masses were in plates or rings, then they would, accord- 
ing to analogy with the magnetic field, place themselves equatorially. If Saturn were 
a magnet as the earth is, and his ring composed of diamagnetic substances, the 
tendency of the magnetic forces would be to place it in the position which it actually 
has. 
2451. It is a curious sight to see a piece of wood, or of beef, or an apple, or a bottle 
of water repelled by a magnet, or taking the leaf of a tree and hanging it up between 
the poles, to observe it take an equatorial position. Whether any similar effects 
occur in nature among the myriads of forms which, upon all parts of its surface, are 
surrounded by air, and are subject to the action of lines of magnetic force, is a ques- 
tion which can only be answered by future observation. 
2452. Of the interior of the earth we know nothing, but there are many reasons 
for believing that it is of a high temperature. On this supposition I have recently 
remarked, that at a certain distance from the surface downwards, magnetic sub- 
stances must be entirely destitute, either of the power of retaining magnetism, or 
becoming magnetic by induction from currents in the crust or otherwise*. This is 
evidently an error; that the iron, &c. can retain no magnetic condition of itself, is 
* Philosophical Magazine, 1845, vol. xxvii. p. 3. 
