The inland navigation of India is, however, chiefly carried on upon the great rivers—the Indus, the Ganges, the Brahmaputra. Taking the limit of the Ganges, and Jumna to the west and south, the Brahmaputra and Megna to the east, the country intersected by navigable rivers, &c., may be computed as covering an area exceeding 180,000 square miles. There is an uninterrupted navigation of 1000 miles up the Indus from the sea to Lahore, which is situated on the Ravee, or Hydrastes, one of the most meandering of the five Punjab rivers or branches composing the Chenab. But, owing to the numerous shallows and sandbanks in some parts of the Indus, this extensive navigation can only be said to be open to the flat-bottomed boats of the country, which draw about four feet of water. There are, however, few rivers on which steam could be used with better effect than on the Indus, which is said to discharge four or five times as much water as the Ganges. It has no rocks nor rapids, and, unless when swollen, the current does not exceed 2½ miles an hour. The swell commences about the end of April, increases till July, and disappears altogether in September. There are many canals connected with the Indus, but they are principally for the purpose of irrigation, and the greater part of them, being mostly natural creeks, have no water except during the swollen state of the river. Such canals intersect the Delta, and are likewise pretty numerous between the latitudes of 26° 20´ and 28°, particularly on the west side of the river; but the most ancient artificial canals connected with this river seem to belong to the Punjab district.