The difference between Despair — Figurehead

The first wreck indicates the destruction of a ship; the second the ruin of a ship's figurehead for all her life until the ship crashed, and her mind can finally rest without fear (and without hope). People cannot read the figurehead's mind from her eye. Somehow Dickinson compared her life with a figurehead, and her seclusion with ship wreck.

The difference between Despair ¹
And Fear－is like the One
Between the instant of a Wreck
And when the Wreck has been－

The Mind is smooth－no Motion－⁵
Contented as the Eye
Upon the Forehead of a Bust－
That knows－it cannot see－

(F.576/J.305)

[1] Despair:: a state without hope; a ship wreck ends all hopes including the figurehead's.
[2] Fear:: a state of dread; the fear of a ship's figurehead while sailing. the One:: the ship's figurehead.
[3] instant of a Wreck:: the moment the ship crashed.
[4] wreck:: a person of undermined, shattered _{(OED 7b)}. Wreck has been:: the figurehead has been ruined for all her life.
[5] Mind, no Motion:: mind, the head of the figurehead now kept still.
[6] Contented:: satisfied since the figurehead can rest after the ship wreck.
[7] Bust:: a sculpture on the ship's head, a figurehead.
[8] cannot see:: the bust's eye cannot see like human, and human cannot understand the bust's mind from her eye.

In this breeze a heavy sea struck the bows and cutwater, and with a most singular result, for it carried away the crown of our figure-head from the forehead upwards; and the ominous remark of the person who reported the circumstance to the officer of the watch was, "Sir, she had lost her brains." ─ A Diary of the Wreck of His Majesty's Ship Challenger (1836)