Hi,

The version titled "Pretty Polly" in West Virginia Folklore - Vol. 7, no. 4, pages 57-59 (Summer 1957) as pointed out by Brian Peters is a composite ballad. The end of the ballad (stanza 8 onward) is from "The Sailor and the Ghost" an 1805 British broadside (Harding B10(68), Bodleian Collection) found in the US, Canada, and UK. Other names include "The Sailor's Tragedy," "The Sea Ghost," "The Dreadful Ghost," and "The Ghost So Grim." Here are the corresponding ending stanzas from The Universal Songster, or Museum of Mirth vol. 2, George Routledge and Sons, London, New York.

The Sailor and the Ghost of His Deserted Dearie (excerpt)

10. Down on the deck this young man goes,
And to his captain his mind disclosed;
There is a spirit coming hence,
I pray you, stand in my defense.

11. Upon the deck the captain goes,
And there he spied a fatal ghost;
Ghost, -"Captain," said she, "you must and can
With speed help me to such a man."

12. Capt. - "In St. Helen's this young man died,
And in St. Helen's his body lies."
Ghost, -"Captain," said she, "do not say so,
He is dwelling down in your ship below.

13. "And if you stand up in his defense,
A mighty storm I will send hence;
Will cause your men and you to weep;
And leave you, sleeping, in the deep."

14. Down from the deck this captain goes,
And brought this young man to his foes.
She fixed her eyes on him so grim,
Which made him tremble, ev'ry limb.

15. "It was well known I was a maid,
When first by you I was betrayed;
I am a spirit, come for thou,
You balked me once, But I'll have you now."

16. Then, to preserve both ship and men,
Into the boat they forced him then;
The boat sunk down in a flame of fire,
Which made the sailors all admire.