What is Ishmael satirizing in the last scene of chapter 35 "The Masthead" in Melville's Moby Dick?

Chapter 35 of Moby Dick finds Ishmael
engaged in metaphysical reverie at he narrates his experience of standing at the
masthead as lookout for whales.  Satire is prevalent throughout this chapter as, for
instance, he notes at the chapter's beginning that whale ship captains insisted that the
mastheads were manned to the very last moments of the
voyage,

not
till her sky-sail poles sail in among the spires of the port, does she altogether
relinquish the hope of capturing one whale
more.

Later, Ishmael wryly
attributes "the business of standing mast-heads" to the Babylonians with their tower.
But, at the chapter's end, after he has described his reverie in the masthead in which
he contemplates metaphysical questions, and, while doing so, probably misses the
sighting of whales, he satirizes himself as he cautions captains against
hiring  “romantic, melancholy, and absent-minded young men,” who are likely to miss
whales in the vicinity.  He satirically alludes to himself
as

a
sunken-eyed young Platonist [who] will tow you ten wakes round the world, and never make
you one pint of sperm the
richer.

In another satiric
allusion, Ishmael calls himself Child Harold, Lord Byron's world-weary young man who
seeks adventure and distraction in foreign lands.  Finally, Ishamel's satire extends to
his Platonic desire to find meaning in the universe and, in so doing, loses his identity
by immersing himself so much in metaphysical reflection that he loses sight of any
whales. Ishmael describes himself as in an "opium-like" listlessness
with

the
mystic ocean at his feet for the visible image of that deep, blue, bottomless soul,
pervading mankind and nature; and every strange, half-seen, gliding, beautiful thing
that eludes him; ....[that] seems to him the embodiment of those elusive thoughts that
only people the soul flitting through
it.

Finally, Ishamel mocks
himself as a Pantheist, declaring that his existence in the masthead becomes only "that
rocking life imparted by a gently rolling ship" until the day he too slip and his life
become much like the life of the idealist Thomas Cranmer (Archbishop of Canterbury), who
was burned as a heretic by Queen Mary. Cranmer immersed his hand into the fire in the
Pantheistic belief that he would be one with nature.