The Shape and Mass of the Iron are of most
_importance in coition_.
Observation has shown above that the shape and mass of the loadstone have
great influence in magnetick coitions; likewise also the shape and mass of
the iron bodies give back more powerful and steady forces. Oblong iron rods
are both drawn more quickly to a loadstone and cleave to it with greater
obstinacy than round or square pieces, for the same reasons which we have
proven in the case of the loadstone. But, moreover, this is also worthy of
observation, that a smaller piece of iron, to which is hung a weight of
another material, so that it is altogether in weight equal to another large
whole piece of iron of a right weight * (as regards the strength of the
loadstone), is not lifted by the loadstone as the larger piece of iron
would be. For a smaller piece of iron does not join with a loadstone so
firmly, because it sends back less strength, and only that which is
magnetick conceives strength; the foreign material hung on cannot acquire
magnetick forces.
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{99} CHAP. XXXI.
On Long and Round Stones.
Pieces of iron join more firmly with a long stone than with a round one,
provided that the pole of the stone is at the extremity and end of its
length; because, forsooth, in the case of a long stone, a magnetick is
directed at the end straight towards the body in which the virtue proceeds
in straighter lines and through the longer diameter. But a somewhat long
stone has but little power on the side, much less indeed than a round one.
It is demonstrable[180], indeed, that at A and B the coition is * stronger
in a round stone than at C and D, at like distances from the pole.
[Illustration]
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