Question

to the sands upon the shore) shall bloom the thunder - blasted tree, or the stricken eagle soar. and all my days are trances, and all my nightly dreams are where thy gray eye glances, and where thy footstep gleams, - in what ethereal dances, by what eternal streams. read stanza ii. a voice from out the future cries, \on! on!\ -- but oer the past (dim gulf!) my spirit hovering lies the dash in the underlined line is used ______. to indicate change in tone or thought to add a second thought or a correction to show interruption of hesitation in speech to set of appositives

Explanation:

In the line "On! on!"--but o'er the Past", the dash is used to indicate a change. The exclamation "On! on!" represents a call to move forward (towards the Future as per the stanza's context). The word "but" after the dash signals a contrast. The speaker's spirit is "hovering" over the Past instead of moving forward as the voice from the Future urges. This shows a shift from the idea of moving ahead (Future) to the focus on the Past, which is a change in thought.

Answer:

to indicate change in tone or thought