RIVER TRENT

 And of the British floods, though but the third I be,
Yet Thames and Severne both in this come short of me,
For that I am the mere of England, that divides
The north part from the south, on my so either sides,
that reckoning how these tracts in compasse be extent,
Men bound them on the north, or on the south of Trent.

From: Michael Drayton: Poly-Olbion, The Sixe and Twentieth Song, 1622.