Once upon a time (I like to be at least as precise as a fairy tale in the matter of dates) there was no Lombardy. And that time was not, geologically speaking, so very remote; for the whole valley of the Po, from Turin to the sea, consists entirely of alluvial deposits--or, in other words, of Alpine mud--which has all accumulated where it now lies at a fairly recent period. We know it is recent, because no part of Italy has ever been submerged since it began to gather there. To put it more definitely, the entire mass has almost certainly been laid down since the first appearance of man on our earth: the earliest human beings who reached the Alps or the Apennines--black savages clad in skins of extinct wild beasts--must have looked down from their slopes, with shaded eyes, not on a level plain such as we see to-day, but on a great arm of the sea which stretched like a gulf far up towards the base of the hills about Turin and Rivoli. Of this ancient sea the Adriatic forms the still unsilted portion. In other words, the great gulf which now stops short at Trieste and Venice once washed the foot of the Alps and the Apennines to the Superga at Turin, covering the sites of Padua, Ferrara, Bologna, Ravenna, Mantua, Cremona, Modena, Parma, Piacenza, Pavia, Milan, and Novara. The industrious reader who gets out his Baedeker and looks up the shaded map of North Italy which forms its frontispiece will be rewarded for his pains by a better comprehension of the district thus demarcated. The idle must be content to take my word for what follows. I pledge them my honour that I'll do my best not to deceive their trustful innocence. It may sound at first hearing a strange thing to say so, but the whole of that vast gulf, from Turin to Venice, has been entirely filled up within the human period by the mud sheet brought down by mountain torrents from the Alps and the Apennines.