s which result when, on its way from
the atmosphere to the earth, it rushes athwart any resisting organic or
inorganic body.

_Magnetism_.--Unlike electricity, which acts with a shock and then
expires, magnetism is a constant quantity, and constant in its action;
and it has this singular property, that it can impart itself as a
permanent force to bodies previously without it. Thus, there being
natural magnets and artificial, we can, by passing a piece of steel over
a magnet, turn it into a strong magnet itself; although we can also,
when it is in the form of a horse-shoe, by a half turn round and then
rubbing it on the magnet, take away what it has acquired, and bring it
back to its original state. The magnetic property is very readily
imparted (by induction, as it is called) to soft iron, but when the iron
is removed from the magnetising body, it parts with the virtue as fast
as it acquired it. To obtain a substance that will retain the power
induced, we must make some other election; and hard steel is most
serviceable for conversion into a permanent magnet.

The properties of the magnet are best observed in magnetised steel; and
when we proceed to test its magnetic power, it will be found that it is
most active at the extremities of the bar, which are hence called its
poles, and hardly, if at all, at the centre; that while both poles
attract certain substances and repel others, the one always points
nearly north and the other nearly south when the bar is horizontally
suspended; and that, when we break the bar into two or any number of
pieces, however small, each part forms into a complete magnet with its
virtue active at the poles, which, when suspended, preserves its
original direction; so that of two particles one is, in that case,
always north of the other; nay, it is probable that each of these has
its north pole and its south, as constant as those of the earth itself,
which, too, is a large magnet.

The magnet acts through media and at a distance, as well as in contact;
and it has an especial attraction for iron, the more so when the
conducting medium is solid, such as a table; and so when the magnet is
horizontally suspended, or poised, in the vicinity of iron, its tendency
to point north and south is seriously disturbed. The disturbance of the
bar, or needle, in such a case, is called its _deflection_; and it is
corrected by so placing a piece of soft iron or another magnet in its
neighbourhood as to neutral