Aerossîr

The Aerossir (S. "River of Lake-foam", Os. "Airossir") was a small river (135 miles) forming the eastern boundary of Rónalindon with Siragale or Siranwaith. It flew through the Tumnogoth Iaur. Tribuitaries included the Nogothir and Belechir. Its name refered to the lake which was its source, and to the turmoil with which the water thundered to the bay. The river was a formidable obstacle to invasion, as even its fords were swift and treacherous.