Lucretius, De Rerum Natura
William Ellery Leonard, Ed.

     It happens, too, at times that nature of iron
Shrinks from this stone away, accustomed
By turns to flee and follow. Yea, I've seen
Those Samothracian iron rings leap up,
And iron filings in the brazen bowls
Seethe furiously, when underneath was set
The magnet stone. So strongly iron seems
To crave to flee that rock. Such discord great
Is gendered by the interposed brass,
Because, forsooth, when first the tide of brass
Hath seized upon and held possession of
The iron's open passage-ways, thereafter
Cometh the tide of the stone, and in that iron
Findeth all spaces full, nor now hath holes
To swim through, as before. 'Tis thus constrained
With its own current 'gainst the iron's fabric
To dash and beat; by means whereof it spues
Forth from itself- and through the brass stirs up-
The things which otherwise without the brass
It sucks into itself. In these affairs
Marvel thou not that from this stone the tide
Prevails not likewise other things to move
With its own blows: for some stand firm by weight,
As gold; and some cannot be moved forever,
Because so porous in their framework they
That there the tide streams through without a break,
Of which sort stuff of wood is seen to be.
Therefore, when iron (which lies between the two)
Hath taken in some atoms of the brass,
Then do the streams of that Magnesian rock
Move iron by their smitings.