Converting poetry to prose

Question

The poem describes a situation when three witches (Old Goody Jones, Goody Price, and Madge Gray) and a man (Robin) stole into the vicarage's cellar and indulged in revelry. These thieves laughed so loud that all the members of the vicarage awake and head to the cellar.

The next part goes...

On, on to the cellar! away! away!

On, on, to the cellar without more delay!

The whole posse rush onwards in battle array.

Conceive the dismay of the party so gay,

Old Goody Jones, Goody Price, and Madge Gray,

When the door bursting wide, they descried the allied

Troops, prepared for the onslaught, roll in like a tide,

And the spits, and the tongs, and the pokers beside! —

Can I change the bolded part into 'while Old Goody Jones, Goody Price, and Madge Gray were conceiving the dismay of the party (the whole posse) so gaily'?

I leave a link to the whole text here. https://ebooks.adelaide.edu.au/i/ingoldsby/thomas/ingoldsby_legends/chapter9.html

Answer 1

No.

"Conceive" here is in the imperative form, an instruction to the reader. The "party so gay" refers to the revellers in the cellar ("gay" here meaning happy or lively). You might rephrase it as:

Imagine the dismay of Old Goody Jones, Goody Price, and Madge Gray, partying so gaily, when ...

(Also, I'm not quite sure what you mean by "can I change". If you're just asking about the meaning, in plainer English, of the quoted text, then you can understand it as above. If you want to quote the poem somewhere, then of course you need to preserve the original text in the quote.)