The great waterway of Austria is the Danube, which rises in the Black Forest, at an elevation of about 3600 feet above the sea, and drains an area of 316,000 square miles, its total length being 1750 miles. Three hundred tributaries, or more, feed this noble river, the seven more important streams having a length of 2900 miles, and draining about one-half of the whole extent of the Danube Basin. At Ulm, 130 miles from its source, the Danube becomes navigable for flat-bottomed boats. In its lower reaches it is traversed by an almost innumerable fleet of steamers and barges, which are the main means of communication between this part of Europe and the Black Sea. _Danube Regulation Works._—The improvement of the channel of the Danube, near Vienna, is one of the most important river engineering works of modern times. A new channel, 10 miles in length, has brought the river 1½ mile nearer to the city, and at a ground depth of 10 to 12 feet below ordinary low-water level, at a cost of 3,250,000_l._ The principal object of the scheme was to protect Vienna from floods, but it has also considerably assisted navigation. Around Vienna the ground is generally flat, and the Danube, with various branches, was, in times of flood, accustomed to inundate the country for many miles round about, doing a great deal of damage both to the city and its suburbs. In order to remedy this condition of things, a commission was appointed which proposed to collect all the branches of the Danube into one channel. The plan attached hereto shows the character of the undertaking. The new channel is nearly 9½ miles in length. It starts from Nussdorf at the foot of the well-known hill called the Kahlenberg, and passes through the flat lands of the Prater, or great public park of Vienna, with a slight curve towards the city, in order that the navigable channel, holding generally to the outside of the curve, should be nearest Vienna, and as close to it as possible, thereby facilitating the shipping on the quays. [Illustration: PLAN OF DANUBE IMPROVEMENT WORKS.] [Illustration: DANUBE IMPROVEMENT WORKS.]