I am not sure that I can draw an exact line between wit and humor... I am quite positive that of the two, humor is the more comfortable and more livable quality. Humorous persons, if their gift
is genuine and not a mere shine upon the surface, are always agreeable companions and they sit
through the evening best. They have pleasant mouths turned up at the corners. To these corners
the great Master of marionettes has fixed the strings and he holds them in his nimblest fingers to
twitch them at the slightest jest. But the mouth of a merely witty man is hard and sour until the
moment of its discharge. Nor is the flash from a witty man always comforting, whereas a
humorous man radiates a general pleasure and is like another candle in the room.
I admire wit, but I have no real liking for it. It has been too often employed against me, whereas
humor is always an ally. It never points an impertinent finger into my defects. Humorous persons
do not sit like explosives on a fuse. They are safe and easy comrades. But a wit's tongue is as
sharp as a donkey driver's stick. I may gallop the faster for its prodding, yet the touch behind is
too persuasive for any comfort.

Wit is a lean creature with sharp inquiring nose, whereas humor has a kindly eye and
comfortable girth. Wit, if it be necessary, uses malice to score a point--like a cat it is quick to
jump--but humor keeps the peace in an easy chair. Wit has a better voice in a solo, but humor
comes into the chorus best. Wit is as sharp as a stroke of lightning, whereas humor is diffuse like
sunlight. Wit keeps the season's fashions and is precise in the phrases and judgments of the day,
but humor is concerned with homely eternal things. Wit wears silk, but humor in homespun
endures the wind. Wit sets a snare, whereas humor goes off whistling without a victim in its
mind. Wit is sharper company at table, but humor serves better in mischance and in the rain.
When it tumbles, wit is sour, but humor goes uncomplaining without its dinner. Humor laughs at
another's jest and holds its sides, while wit sits wrapped in study for a lively answer. But it is a
workaday world in which we live, where we get mud upon our boots and come weary to the
twilight--it is a world that grieves and suffers from many wounds in these years of war: and
therefore as I think of my acquaintance, it is those who are humorous in its best and truest
meaning rather than those who are witty who give the more profitable companionship... -- On
the Difference Between Wit and Humor by Charles S. Brooks

How does Brooks use contrast to convey a specific purpose in the excerpt?