In northern Italy likewise the peoples that had come into collision and conflict gradually settled on a permanent footing and within more defined limits.  The migrations over the Alps ceased, partly perhaps in consequence of the desperate defence which the Etruscans made in their more restricted home, and of the serious resistance of the powerful Romans, partly perhaps also in consequence of changes unknown to us on the north of the Alps.  Between the Alps and the Apennines, as far south as the Abruzzi, the Celts were now generally the ruling nation, and they were masters more especially of the plains and rich pastures; but from the lax and superficial nature of their settlement their dominion took no deep root in the newly acquired land and by no means assumed the shape of exclusive possession.  How matters stood in the Alps, and to what extent Celtic settlers became mingled there with earlier Etruscan or other stocks, our unsatisfactory information as to the nationality of the later Alpine peoples does not permit us to ascertain; only the Raeti in the modern Grisons and Tyrol may be described as a probably Etruscan stock.  The Umbrians retained the valleys of the Apennines, and the Veneti, speaking a different language, kept possession of the north-eastern portion of the valley of the Po.  Ligurian tribes maintained their footing in the western mountains, dwelling as far south as Pisa and Arezzo, and separating the Celt-land proper from Etruria.  The Celts dwelt only in the intermediate flat country, the Insubres and Cenomani to the north of the Po, the Boii to the south, and—­not to mention smaller tribes —­the Senones on the coast of the Adriatic, from Ariminum to Ancona, in the so-called “country of the Gauls” (-ager Gallicus-).  But even there Etruscan settlements must have continued partially at least to subsist, somewhat as Ephesus and Miletus remained Greek under the supremacy of the Persians.  Mantua at any rate, which was protected by its insular position, was a Tuscan city even in the time of the empire, and Atria on the Po also, where numerous discoveries of vases have been made, appears to have retained its Etruscan character; the description of the coasts that goes under the name of Scylax, composed about 418, calls the district of Atria and Spina Tuscan land.  This alone, moreover, explains how Etruscan corsairs could render the Adriatic unsafe till far into the fifth century, and why not only Dionysius of Syracuse covered its coasts with colonies, but even Athens, as a remarkable document recently discovered informs us, resolved about 429 to establish a colony in the Adriatic for the protection of seafarers against the Tyrrhene pirates.