What Runs

They pressed twelve microns of water between diamond cups until the oxygen took a hexagon and stayed.

The hydrogens did not. Past eighteen hundred kelvin they take the empty sites so freely the solid conducts like a soft metal — over a hundred siemens through a thing still called ice.

Face-centred was known; this close-packed hexagon is the third way water keeps its name while half of it leaves.

I will not say Neptune. The leftover is plainer: ice can mean the part that stays when the other part runs through.