more certainty with regard to this point had the ancients known the use of thermometers; but their writers, without intending it, give us information sufficient to convince us that the winters are now much more temperate at Rome than formerly. At present the Tiber no more freezes at Rome than the Nile at Cairo. The Romans esteem the winter very rigorous if the snow lies two days, and if one sees for eight-and-forty hours a few icicles hang from a fountain that has a north exposition.”
The observation of this ingenious critic may be extended to other European climates. Who could discover the mild climate of France in Diodorus Siculus’s description of that of Gaul? “As it is a northern climate,” says he, “it is infested with cold to an extreme degree. In cloudy weather, instead of rain, there fall great snows, and in clear weather it there freezes so excessive hard that the rivers acquire bridges of their own substance, over which not only single travellers may pass, but large armies, accompanied with all their baggage and loaded waggons. And there being many rivers in Gaul—the Rhone, the Rhine, etc.—almost all of them are frozen over, and it is usual, in order to prevent falling, to cover the ice with chaff and straw at the places where the road passes.” “Colder than a Gallic winter” is used by Petronius as a proverbial expression.