Adriatic Sea, the portion of the Mediterranean lying between Italy on the W. and Turkey and Austria on the E., takes its name from the city of Adria. Its length from the strait of Otranto (which connects it with the Ionian sea) to the head of the gulf of Trieste is about 500 m.; its average width about 130 m., which, northward from the mouth of the Po, is reduced to about 60 m. by the peninsula of Istria. The Adriatic receives few rivers of importance, except the Adige and the Po. The western coast is generally flat and swampy; its harbors are few and poor. The eastern shores are steep and rocky, and the numerous islands along the Dalmatian coast furnish vessels a safe shelter from storms. The northwestern part of the Adriatic is known as the gulf of Venice, the northeastern as the gulf of Trieste. On the Neapolitan coast lies the gulf of Manfredonia, on the Dalmatian the gulf of Cattaro, and on the Albanian that of Drino. During summer the navigation of the Adriatic is usually free from danger, but the S. E. winds that blow in winter produce disastrous shipwrecks. Its depth between Dalmatia and the outlets of the Po is 22 fathoms; but opposite Venice, and in a considerable portion of the gulf of Trieste, it is less than 12 fathoms. To the southward it deepens rapidly.

Its waters are more salt than those of the Atlantic. The tides are almost imperceptible. There can be little doubt that the dimensions of the Adriatic were formerly much greater than at present, and that they have been contracted by the deposits of mud made by the streams that empty into it. On the western coast several lagoons produced by sand bars are being rapidly transformed into meadows by this process. The original depth of the Adriatic has likewise been diminished by the accumulations of sandy marl and testaceous incrustations at the bottom.