Editorial question:
Butler says : He(River Scamander) lifted his waters into a high crest and cried aloud to Simoeis saying, "Dear brother, let the two of us unite to save this man, or he will sack the mighty city of King Priam, and the Trojans will not hold out against him.

Greek says:
[24ὑψόσ' ἀειρόμενος,24] Σιμόεντι [25δὲ κέκλετ' ἀΰσας:25]
IL.21.307 gathered it to a crest, and called aloud upon Simoeis:

IL.21.308 [26φίλε κασίγνητε26] σθένος ἀνέρος ἀμφότεροί περ
IL.21.308 'Beloved brother, let even the two of us join to hold back

IL.21.309 σχῶμεν, ἐπεὶ [27τάχα [28[29[30ἄστυ27] μέγα30] [31Πριάμοιο29] ἄνακτος28]31]
IL.21.309 the strength of a man, since presently he will storm the great city

IL.21.310 ἐκπέρσει, Τρῶες δὲ κατὰ μόθον οὐ μενέουσιν.
IL.21.310 of lord Priam. The Trojans cannot stand up to him in battle.

When Butler says "save" he doesn't mean "save Achilles" he means "stop Achilles". Should we make this more clear?