“ Petersburg, flow into the gulf of Finland, the first by the river Svir into Lake Ladoga, and the latter by the Neva into the bay of Cronstadt. The bed of the gulf is of calcareous rock, in some parts compact and naked, in others covered and filled with shells. Occasional points of granite are intermingled with this general character. The depth of water is nowhere great, and is least along the southern coast, of which the submerged descent is gradual. The northern shore is much hemmed in with islands and granite rocks. ”