τί … ἀφήσει τέλος; "what end (event) will (the lightning) bring forth?" For ἀφιέναι as="to emit," "produce from one's self," cp. Arist. 6. 14 ἀφιᾶσι τὸ κύημα,...τῆς θηλείας ἀφιείσης τὸ ᾠόν. This use, which was common, suggests how the word might be figuratively said of the storm giving birth to some disastrous issue. We need not, then, seek a correction (as ἐφήσει or ἐφήξει).

μὰν, "verily," here nearly=an exclamation, such as "ah!" Cp. on 182.