Figure C17 EXTREMES

From such a distant past, the present seems

To dazzle and confuse us. Rocky walls

Rough-hewn glow white in horizontal beams

Of the low sun, which e’en at twilight spalls

Hot ions from the stone on which it falls,

Yet at our feet the floor is all of ice.

The sunlight sweeps: at intervals, it stalls

As MERCURY turns three times, orbits twice,

Its polar craters in eternal winter’s vise.