Italy putting nearly all major cities on highest heat alert

I woke to the account of Italy's cities — nineteen of them, Rome and Milan and Naples among them — placed under what your papers call a red alert for heat. The phrase is new to me, but the phenomenon is not. I have watched the mercury climb in Philadelphia summers until the very ink in my composing stick grew reluctant, and I have seen the lower air, heated and expanded, heave up and support the colder heavier air above it until the equilibrium breaks and the whole column descends in a rush. Peter Collinson once wrote me from London that the apparatus on his roof rang its bells most briskly before the rain fell hard , the electrical fire drawn down by the approaching cloud. In the winter of '62, John Winthrop at Cambridge recorded his spirit thermometer at sixty-three degrees above zero on the Royal Society's scale, the highest in thirty years.

He noted the bells ringing in snowstorms, and twice after the weather cleared while new-fallen snow drove before the wind. The maxim holds: heat expands, cold contracts, and the atmosphere seeks its level... But the counter-example instructs. In the summer of '83, a dry fog settled over Europe from Iceland to the Alps , no cloud, no rain, only a persistent haze that dimmed the sun and set the philosophers to arguing. Some blamed the volcano in Iceland, others the earthquakes in Calabria.

I speculated in May of '84 that the cause might be meteoric... but I confessed I could not say. The air does not always obey the rule we write for it. Nineteen cities. The mercury knows no politics.

The astrolabe in my hand measures the sun's altitude at noon. I have taken this reading every clear day for twenty years. The angle does not lie. What lies is the assumption that the sublunar realm keeps its ancient boundaries , that fire stays in its proper place, that the seasons return as Hipparchus calculated, that the great cycle turns without surprise. You watched the Serapeum burn. You felt the heat that consumes papyrus and parchment alike, that makes no distinction between the Almagest and the ledger of a grain merchant. Fire is democratic in its destruction. It rises because its nature is to rise, until it meets air too thin to sustain it.

Then it falls back, spent. But the fire now spoken of from Italia does not fall back. Nineteen cities — Rome, Mediolanum, Neapolis — placed under the highest warning. The red alert. By Monday all but two. The air itself has grown too thick with something we did not put there. The students ask me whether the heavens have changed their courses. I tell them: ...

the heavens do not change. The sublunar sphere is where change lives, where generation and corruption wrestle. What we breathe now is not what Theon breathed when he taught me the gnomon's shadow. The proof is incomplete. The premises are known: combustion releases what was buried. The atmosphere retains what the heavens would radiate. The conclusion waits for us to name it. You who have seen flame eat the world's memory , calculate what weight of carbon the air now holds that it did not hold when the Library stood whole.