LADOGA, a lake of northern Russia and Finland (formerly Nevo), the boundary between the two countries running in a north easterly direction across the lake, which lies between 59° 56' and 61° 46' N., and 29° 53' and 32° 50' E. It has the form of a quadrilateral, elongated from north-west to south-east. Its east ern and southern shores are flat and marshy, the north-western craggy and fringed by numerous small rocky islands, the largest of which are Valamo and Konnevitz, lying in the Finnish section, together having an area of 14 sq.m. Ladoga is 7,000 sq.m. in area, that is, 31 times as large as the Lake of Geneva; but, its depth being less, it contains only 19 times as much water as the Swiss lake. The greatest depth, 73o ft., is in a trough in the north-western part, the average depth not exceeding 25o to 35o ft. The level of Lake Ladoga is 55 ft. above the Gulf of Finland, but it rises and falls about 7 ft., according to atmospheric con ditions, a phenomenon very similar to the seiches of the Lake of Geneva being observed in connection with this.
The western and eastern shores, as well as a narrow strip on the southern shore, consist of boulder clay, south of which runs a ridge of crags of Silurian sandstones. The hills of the north western shore afford a variety of granites and crystalline slates of the Laurentian system, whilst Valamo island is made up of a rock which Russian geologists describe as orthoclastic hyper sthenite.
No fewer than 7o rivers enter Ladoga, pouring into it the waters of numberless smaller lakes which lie at higher levels round it. The Volkhov, which conveys the waters of Lake Ilmen, is the largest ; a hydro-electric station on the Volkhov was opened in 1926 with a capacity of 56,000 kilowatts. Lake Onega discharges its waters by the Svir; and the Saima system of lakes of eastern Finland contributes the Vuoxen and Taipale rivers; the Syas brings the waters from the smaller lakes and marshes of the Valdai plateau. Ladoga discharges its surplus water by means of the Neva, which flows from its south-western corner into the Gulf of Finland, rolling down its broad channel 104,00o cu.ft. of water per second.
The water of Ladoga is very pure and cold; in May the surface temperature does not exceed 36° and even in August it reaches only 5o° and 53°, the average yearly temperature of the air at Valamo being 36.8°. The lake begins to freeze in October, but it
is only about the end of December that it is frozen in its deeper parts; and it remains ice-bound until the end of March, though broad ice-fields continue to float in the middle of the lake until broken up by gales. Only a small part of the Ladoga ice is dis charged by the Neva ; but it is enough to produce in the middle of June a return of cold in Leningrad. The thickness of the ice does not exceed 3 or 4 ft.; but during the alternations of cold and warmer weather, with strong gales, in winter, stacks of ice, 7o to 8o ft. high, are raised on the shores and on the icefields. The water is in continuous rotatory motion, being carried along the western shore from north to south, and along the eastern from south to north. The vegetation on the shores is poor; immense forests, which formerly covered them, are now mostly destroyed. But the fauna of the lake is somewhat rich; a species of seal which inhabits its waters, as well as several species of arctic crustaceans, recall its former connection with the Arctic ocean. The fresh water Diatomaceae which are found in great variety in the ooze of the deepest parts of the lake. also have an arctic character.
Fishing is very extensively carried on. Navigation, which is practicable for only i8o days in the year, is rather difficult owing to fogs and gales, which are often accompanied, even in April and September, with snow-storms. The prevailing winds blow from north-west and south-west; north-east winds cause the water to rise in the south-western part, sometimes 3 to 5 ft. Steamers ply regularly from Leningrad to the mouth of the Svir, whence they go up that river to Lake Onega and Petrozavodsk; and small vessels transport timber, firewood, planks, iron, kaolin, granite, marble, fish, hay and various small wares from the north ern shore to Schliisselburg, and thence to Leningrad. Navigation on the lake being too dangerous for small craft, canals with an aggregate length of 104 m. were dug in 1718-31, and others in 1861-86 having an aggregate length of 'or m. along its southern shore, uniting with the Neva at Schliisselburg the mouths of the rivers Volkhov, Syas and Svir, all links in the elaborate system of canals which connect the upper Volga with the Gulf of Finland.