What is one of the principal rivers of Hades, in the channel of which fire flowed instead of water. Fierce Phlegethon, Whose waves of torrent fire inflame with rage. Milton called?

phlegethon — One of the principal rivers of Hades, in the channel of which fire flowed instead of water. Fierce Phlegethon, Whose waves of torrent fire inflame with rage. Milton. (Webster's 1913.)

Sources