Not P but Moby-Dick (83)

[Mike Jing]

>From Chapter 104:

One often hears of writers that rise and swell with their subject, though
it may seem but an ordinary one. How, then, with me, writing of this
Leviathan? Unconsciously my chirography expands into placard capitals. Give
me a condor’s quill! Give me Vesuvius’ crater for an inkstand! Friends,
hold my arms! For in the mere act of penning my thoughts of this Leviathan,
they weary me, and make me faint with their outreaching comprehensiveness
of sweep, as if to include the whole circle of the sciences, and all the
generations of whales, and men, and mastodons, past, present, and to come,
with all the revolving panoramas of empire on earth, and throughout the
whole universe, not excluding its suburbs.

What does "rise and swell" mean here?