The Properties of Magnets

by Rene Descartes Icon

4 minutes • 804 words

[4.145] Enumeration of the properties of magnetic force.

All these properties follow from the principles of Nature explained above in such a way that, even if I did not consider those magnetic properties that I undertook to explain here, I would still judge them to be true.

However, from now on, we will see that through the aid of these principles, a reason can be given so fittingly and clearly for all these properties that it seems sufficient to persuade that they are true, even if we do not know how they follow from the principles of Nature.

The magnetic properties that are usually noted by their admirers can be referred to these headings.

There are 2 poles in a magnet

one is everywhere directed towards the Earth’s northern pole
the other towards the southern pole.

These magnetic poles incline in various ways towards its center, depending on their different places on the earth.
If 2 magnets are spherical, one turns towards the other in the same way as each of them turns towards the Earth.
After they have thus met, let them go to the opposite side.
But if they are detained in the opposite situation, they should flee from each other.
But if a magnet is divided by a plane, lines drawn parallel through its poles, the parts of the segments, which were previously joined, also repel each other
But if it is divided by a plane, cutting a line drawn through the poles at right angles, 2 points must first be contiguous to the poles of opposite virtue, one in one, the other in another segment.
One magnet only has 2 poles, one southern, the other northern.

Yet in each one of its fragments, 2 similar poles are also found; insomuch that his power, in so far as it is seen to be different by reason of the poles, is the same in any part and in the whole.

The iron receives this force from the magnet only when it is moved to it.
The magnet receives the iron in various ways.

An oblong iron, in any way moved by a magnet, always receives it according to its length.
A magnet loses nothing of its own power, although it shares it with steel.
Steel is quickly united with the iron magentically.

But the longer the time passes, the steel is more strengthened in it.

The hardest steel will receive iron more and will hold it more steadily than the lighter iron.
More is communicated to it by a more perfect magnet, than by a less perfect one.
The earth itself is also strong. It shares something of its own with iron.
This force in the Earth, the greatest magnet, appears less strong than in most other lesser ones.
That a needle, touched by a magnet, turns its ends towards the earth in the same way as the poles of the magnets.
That they do not turn exactly towards the poles of the Earth, but in various places they deviate from them.
That this decline may change with time.
That there is nothing, as some say, or perhaps that it is neither the same nor so great, in a magnet erected perpendicularly above one of its poles, as in one whose poles are equally distant from the earth.
That magnet draws iron.
That armed magnets can withstand much more iron than bare ones.
That its poles, although opposite, help each other in turn to support the same iron.
The rotation of an iron roller, suspended by a magnet, in either direction is not hindered by the magnetic force.
That the force of one magnet may be variously increased or diminished, by the application of various other magnets or of iron to it.
That a magnet, however strong it may be, cannot draw back iron, removed from it, by the contact of another weaker magnet.
As against a weak magnet, or a small piece of iron, /287/ it often separates another piece of iron contiguous to it from a stronger magnet.
That the pole of the magnet, which we call Southern, supports more iron in these Boreal regions than that which we call Boreal.
The filing of iron around one or more magnets arranges itself in certain ways.
That the iron plate, attached to the pole of the magnet, deflects the force of the iron being drawn or turned.
That the same should not be hindered by the interposition of any other body.
A magnet remaining turned towards the Earth or other neighboring magnets in a different way than it would turn spontaneously, if there were nothing to hinder its motion, loses its force with the success of time.
These things are also diminished by rust, humidity, and situation, and are removed by fire; but not by any other reason known to us.