an agony in eight fits

I just found this gorgeous little book, so I scanned it

But oh, beamish nephew, beware of the day,
If your snark be a Boojum! For then

You will softly and suddenly vanish away,

And never be met with again!

"Tis the note of the Jubjub! Keep count, I entreat;
You will find I have told it you twice.
Tis the song of the Jubjub! The proof is complete,
If only I've stated it thrice."

Without rest or pause - while those frumious jaws
Went savagely snapping around -
He skipped and he hopped, and he floundered and flopped,
Till fainting he fell to the ground.