Not that I really know what I'm talking about here.... (someone who knows the proverb please explain!!)
I take it to mean that it is an effortless mixing... a natural, effortless event like inertia or gravity....
Interesting, that does seem to imply something about the characters that we might not have assumed.
We can't say Jack and Ennis come together like milk and water, since it was not effortless, it was awkward--even dangerous--for some time in the FNIT; and then, it was more like gunpowder and fire than milk and water.....
So I guess what I get out of it is that it was the easiest thing to do, the path of least resistance for Jack and Lureen to get together. And, despite his face during the dance, by the time they get into the back seat, Jack certainly seems like a natural....
