with the Romans; and, but their jealousy of each other, might for ever have defied the Roman arms. One of the branches of the Po was the Draria, which, at this period poured down, or was supposed to pour down gold-dust in its sands; which the Salassi endeavoured to secure to themselves before it reached the country of Insubria. The Insubres, incapable of supporting their own imagined right, appealed to the consul Appius Claudius Pulcher, who readily took advantage of the appeal, and immediately invaded the Salassi. At first, however, he was unsuccessful, being defeated with a loss of five thousand men: though upon a second battle he triumphed to an equal extent, and at length gratified himself and his countrymen by equally reducing both nations to a state of subjection.

This noble river, rises from mount Vesula, or Viso, on the very confines of France and Italy, nearly in the parallel of mount Dauphin, in Dauphiné, and Saluzzo, in Piedmont, being almost central between them, at the distance of about 18 English miles from each. Thus descending from the centre of the western Alps, the Po passes to the N. E. of Saluzzo, by Carignan, to Turin; receiving even in this short space many rivers, as the Varrita, Maira, and Grana from the south; and from the N. the Felice, Sagon and others. Most of these streams having had a longer course than what is called that of the Po, the Maira, for instance, might perhaps be more justly regarded as the principal river: nay the Ta naro, which flows into the Po, some miles below Alexandria, might perhaps claim, in the river Stura, a more remote source than the Po itself. After leaving the walls of Turin, the Po receives innu. merable rivers and rivulets from the Alps in the N. and the Appennines in the S. Among the former may be named the Doria, the Tesino, the Adda, the Oglio, the Mincio: to the east of which the Adige, an independent stream, descends from the Alps of Tyrol, and refusing to blend his waters with the Po pursues his course to the gulph of Venice. From the south the Po first receives the copious Alpine river Tanaro, itself swelled by the Belba, Bormida, and other streams: the other southern rivers are of far less consequence, but among them may be named the Trebbia, the river of Parma and Panaro, which joins the Po at Stellato, on the western frontier of the former territory of Ferrara. The course of the Po may be comparatively estimated at about 300 British miles; so that when Busching pronounces it the second river in Europe, after the

Danube, he must have forgotten the Rhine, the Elbe, the Oder, the Vistula, not to mention the Loire of France, the Tajo of Spain, and other noble streams! The numerous tributary rivers, from the Alps and Apennines, bring down so much sand and gravel that the bed of the Po has in modern times been considerably raised, so that in many places banks of thirty feet in height are necessary to preserve the country from inundation. Hence hydraulics have been much studied in the north of Italy; and the numerous canals of irrigation delight and instruct the traveller. Perhaps by deepening the chief estuary, and bed of the river, equal service might have been rendered to commerce. In the middle ages maritime combats took place on the Po, between Venice and some of the inlaud powers. It is remarkable that, from Cremona to the sea, there is no capital city founded on the main stream of the Po; and the case was the same in ancient times; an exception to the supposition that every river has some grand city near its estuary *.

9. The Tiber.

This stream immortalized in both prose and verse, and by far the most considerable in the middle or south of Italy, is said to derive its name from Tiberinus, an early Latin king, and direct descendant of Oneus, by Lairnia, who was drowned in its waters in the course of a battle which was fought on its banks.

It rises near the source of the Arno, south east of St. Marino, and passes by Perugia and Rome, to the Mediterranean, which it joins after a course of about 150 miles. It is said to receive not fewer than forty-two rivers or torrents, many of them celebrated in Roman history; as is the Rubicon, a diminutive stream, now the Fiermesino, which enters the Adriatic, about eight British miles to the north of Rimini.

In consequence of these numerous torrents it occasionally overflows its banks; and in an early period of the Roman empire, before its embankment was made sufficiently powerful and lofty, these

* To the N. of Ferrara the Po seems as broad as the Rhine at Dusseldorf, Stolberg, ii. 576: but is probably not above half as deep. Dr. Smith, ii. 360, compares the Po, near Ferrara, to the Maese at Rotterdam, and says it is nearly as wide. That Maese is only a branch of the Rhine.

eruptions were not only frequent but for the most part very destruc tive. Thus in the reign of Trajan, we are told, that it overflowed its banks with prodigious violence, laid great part of the city under water, overturned many houses, and produced so much damage to the adjoining fields as to occasion a severe local famine; and all this, notwithstanding that the emperor had endeavoured to guard against the evil, by canals for carrying off the surplus water in the case of an inundation of the Tiber, Aurelian pursued another plan, and deepened its channel, while he enriched its banks with numerous and extensive wharfs. Still, however, it occasionally produced the same public mischief, and in the reign of Valentinian, overflowed to such a degree that it laid all the lower parts of Rome under water, and the inhabitants were obliged to save themselves upon the hills; where the greater number of them would have perished of hunger had not Claudius, prefect of the city, sent them a seasonable supply of provisions in boats. It was Valentinian who crowned the Tiber with the celebrated bridge, which was at first called the bridge of Gratian, and afterwards of Cestus. It is the Ponto di S. Bartolomeo, or St. Bartholomew's bridge, of the present day.

SECTION IV.

PERIODICAL SPRINGS AND LAKES.

1. Introductory Observations.

AMONG the natural phænomena that the surface of the earth dise plays to us, there are few more curious than those of intermitting or reciprocating fountains or other beds of water; nor is it by any means an easy matter to account for so extraordinary a fact. Aa irregularity of flow is indeed by no means uncommon; most of the boiling springs are subject to it. But there are others that evince almost as regular and periodical influx and reflux as the tides of the ocean; while, not unfrequently, these alterations occur several times in a day or even in an hour. Perhaps the causes are various, and are sometimes subterranean and at others superficial. Generally speaking, springs and lakes of this description have been ascertained to communicate with a lower layer of the same, through pores or apertures of various diameter, which serve equally to carry off the