His fertilising water, Tigris first

Drawn down by earth in covered depths is plunged

And holds a secret course; then born again

Flows on unhindered to the Persian sea.

But warlike Parthia wavered 'twixt the chiefs,

Content to have made them two (20); while Scythia's hordes

Dipped fresh their darts in poison, whom the stream

Of Bactros bounds and vast Hyrcanian woods.

(Editor：science)