Negatives Used Positively

Last time, I wrote about how grammatically correct double negatives ("I don't mean to say I don't like it") are harder to follow than positive statements ("I mean to say, I like it"). Generally when I write, I try to use positive statements about what is instead of talking about what isn't. 

Sometimes, though, negatives can emphasize a point that positives wouldn't make as strongly. Here's a quote from one of British comic P. G. Wodehouse's later novels, the 1974 Jeeves in the Morning:

At a moment like this, with old boyhood friends meeting again [...] you might have expected a good deal of animated what-ho-ing and an immediate picking up of the threads. Of this, however, there was a marked absence.

The second sentence strikes me as a very droll, and much more clever, way of showing how awkward the meeting must have been than just talking about how awkward it was. 

This technique can work in more serious situations, too. Imagine you're writing about a character whose child ("Sally") was gone and there was no expectation of her return. (Dead? Or just gone to a distant college? Keep those two options in mind.) You could write something like:

Everywhere I looked, Sally wasn't.

Note how the "dead" versus "college" options change how hard a sentence like that can hit the reader.

My all-time favorite negative description, though, comes from The Hitchhiker's Guide to the Galaxy by Douglas Adams. Adams is writing about spaceships appearing in the skies all over the world and the effect they had on people.

Many people went straight into shock as their minds tried to encompass what they were looking at. The ships hung in the sky in much the same way that bricks don't.

I find that last bit astonishingly evocative, and I struggle to come up with a positive comparison that would work as well as the negative one does. By using the negative, Adams gets across how wrong it is for the ships to be hanging in the sky like that, and why they are boggling so many minds.

(Oh, and congratulations to reader "Dwarzel" for guessing what my favorite Hitchhiker's quote was.)

Do you have any examples of negatives used positively? Quote them in the comments--I'd love to see them.