The two shores of the Adriatic are totally different in their natural characteristics; the western being almost islandless and destitute of harbours, while the eastern is fringed by an almost continuous chain of islands and possesses several magnificent harbours which communicate with the open sea by narrow channels easily fortified, the rocks rising precipitously from the water along the greater part of the coast, whereas on the Italian side there is an equally continuous strip of alluvial plain between the foothills and the sea.

The Adriatic was once bounded by a kind of ridge stretching from Monte Gargano to Albania. North of this line the depth is much less than in the Ionian Sea. When the surface of the earth sank, the Dalmatian islands were formed by the letting in of the sea. The depth near Parenzo is about 120 ft.; in the Quarnero, near Fiume, 195 ft.; between Cherso and Arbe, 335 ft.; and south-west of the island Zuri (some 24 miles from the mainland), about 700 ft. Depths as great as 335 ft. to 490 ft. are, however, not very common within nine miles of the mainland. In the Bocche di Cattaro the depth near the mouth is 165 ft., but half a mile west of the Punta d'Ostro, 335 ft. North of the line from Monte Gargano to Pelagosa, Cazza, and Curzola it is never as much as 780 ft.; south-east of this line the bottom sinks so much that between Cattaro and Brindisi it reaches a depth of over 5,000 ft. The tide is scarcely perceptible, and the currents are very slight. The land is still sinking, as is proved by the Roman sarcophagi found beneath the water at Vranjic and the submerged roads between Aquileia and Grado; while there are records of the destruction of ancient towns from sudden subsidences, as that of Cissa, near Rovigno. The subsidence has been calculated as about a yard in 1,000 years. Cluverius proves from Ptolemy that in antiquity the name Adriatic only applied to that part of the gulf which lay to the north of a line between Monte Gargano and Durazzo. A passage of Strabo, describing the people of Epirus, runs: "The Adriatic being ended, the Ionian commences, the first shore of which is in the neighbourhood of Epidamnus and Apollonia." When Venice conquered Durazzo the limits of the Adriatic were extended, and it was thenceforth called the Gulf of Venice. In 1859 the almost incredible fact is recorded that it was frozen for several days!

The Austrian provinces which lie along the coast are, commencing at the north, the KÜstenlande, Istria, and Dalmatia. In the first the Julian Alps form a great boundary wall to the plain of the Isonzo, from which the ground rises between Monfalcone and Nabresina to the stony district of the Karst. The Istrian ranges are spurs from this lofty plateau, the chain culminating in Monte Maggiore, north-west of Fiume. All these heights belong to the Julian Alps. Beyond Fiume, southwards, there are three principal mountain chains, all of which have much the same formation of limestone, pale brownish or grey in colour, with fossils and streaks of other colours. The first is the Dinaric Alps or Velebits, a continuation of the Julian Alps. These separate Dalmatia from Bosnia as far as Imoschi, where they enter Herzegovina, finally joining the Montenegrin chain. The chain of the shore commences on the left bank of the Kerka and extends to the Narenta, which cuts it. It runs as far as Trebinje, beyond the river. The Montenegrin mountains, which are so impressive above the Bocche di Cattaro, joining with those of the Herzegovina, make the third chain. The islands and rocks in the sea appear to be submarine branches of the littoral chain; the strata lie in the same direction—in the North Dalmatian islands to the north-west, in the Southern to the west. On the peninsula of Sabbioncello they lie partly in one and partly in the other direction. The former connection between the islands and the mainland is proved by the remains of rhinoceros, horse, and stag in the diluvial bone breccias of Lesina, and the survival of the jackal in Giuppana, Curzola, and Sabbioncello. Geologists hold that the deeply cut bays of Sabbioncello and Gravosa, as well as of the Bocche di Cattaro, and the step-shaped sinkings of the northern and eastern limestone mountains towards the Adriatic basin are signs of the tearing away of the islands from the mainland, perhaps through the destruction of the permeable strata.

These generally show in their forms the craggy and stony character of the Dinaric Alps, rising perpendicularly from the water on the side of the prevailing wind, and without vegetation. On the other side are softer hills and plains with southern vegetation, the aromatic scents from which are carried by the breeze. There are about twenty large islands, some of which are over 30 miles long; but the number may be raised to a hundred by counting in the small ones. They are generally in groups or chains, though some are isolated. The water is generally deep up to the shore, so there are very few sandbanks.

The greater portion of the naked surface of the land is formed of limestone and dolomites, which are closely related: there are also, on the lower levels, grey or red sands, among which schistous loams of uniform colour predominate. These two formations stretch from one end of the province to the other in sloping beds. They are interrupted here and there by loam and schistous clay and horizontal beds of a kind of limestone: below these are lignites and chalky limestone, in which shells are found belonging to a later formation. The oldest formations are the volcanic mountains near Knin and on Lissa. Next follow the trias strata, as under the Velebits and westwards from Sinj, then the sandstone beds, the different eocene beds and alluvial strata, as in the plain of Dernis, north of the Vrana Lake, by Nona and Imoski. The principal characteristic of the Karst district (to which Dalmatia belongs geologically) is the way the water flows, sometimes above, sometimes under ground. Where the woods were cut down to supply the Romans and Venetians with material for constructing their fleets, and where natural afforestation has been stopped by the feeding of sheep and goats, the red earth has either been washed away by the rains or blown away by the winds, so that it is only in the hollows that cultivation can be carried on.

The bitter north wind, the Bora, is the curse of the district. In the island of Arbe it sometimes blows even in June and July, stripping the vineyards as if hundreds of men had been at work, and carrying the salt spray all over the island, to the great detriment of vegetation. It is sometimes strong enough to upset pedestrians, and it is said that if it were not for it, there would be neither winter nor cold in the Dalmatian littoral. On the heights winter begins in November and lasts till April, with heavy snowfalls; but on the coast spring begins in February, and winter only at the beginning of December. The summer, which commences in May, is usually rainless, with the heat tempered by sea-breezes, though at the end of August heavy rains commence, and in autumn the frequent changes of temperature are dangerous. The flora consists of nearly 2,500 species, described by Visiani in his "Flora Dalmatica." The aquatic flora contains nearly 700 varieties, many of the seaweeds being exclusively Dalmatian. Views on the coast of Ragusa, or at Castelnuovo, in the Bocche, resemble those of Sardinia and Sicily. On one side may be seen green meadows, fruit trees, flowing water, cornfields, beechwoods, &c.; on the other, olive groves, thickets of arbutus, hedge plants the height of a tree, myrtles, and bay; on the naked rock aloes grow and the opuntia; in gardens, dwarf and date-palms, unprotected cycas revoluta, and orange and lemon trees; and wide valleys are filled with lofty carob trees—so close are the boundaries between the flora of middle Europe and of the Mediterranean. Almonds flower in December, and peas and beans are often gathered at Christmas. At Cannosa the date-palm ripens its fruit, and flowers are always to be seen. The Euphorbia Dendroides grows as high as in Crete, and rosemary bushes are frequently up to the shoulder of a man. In August the Syrian hibiscus is violet-red and the scarlet-red arbutus fruit hangs till Christmas. On Monte Marjan, near Spalato, where Diocletian had his parks, the sheltered aspect creates a tropical climate. Wild aloes grow 6 ft. high, and in midwinter numbers of field flowers may be picked as if it were spring.