About a mile below the cataracts, the course of the Gotha was again interrupted by a fall called Akerstræum; and at the end of last century a canal 182 feet long, and 36 feet broad, was constructed here, through a bed of rock, until, at the other end of the cataract, the river is clear to Gothenburg. Before the construction of the Gotha Canal, the traffic for Gothenburg was unloaded at the cataracts, carried over the wooden road to the end of the falls by horses, and again put on board vessels which carried it through the Akerstræum Canal to its ultimate destination.[98] At Trolhätta, about 1¼ mile below the point where the river Göta-Elf leaves the Wenner Lake, there occurs a series of falls and rapids, the river descending 108 feet in a length of about 4590 feet. The works which were commenced at this place early in the last century, were well advanced in 1755, when an unusually heavy flood caused much destruction and loss of life, and the abandonment of the works, never since resumed. The intention was to surmount the difference of level, viz., 108 feet, at the falls above mentioned, by three locks only, with a rise of 36 feet each. In the canal, as constructed in 1800, there is a chain of eight locks (still in service), but these being insufficient for the traffic, a second set of eleven were constructed alongside the former in 1844. These are cut in the solid granite. There are sixteen locks in all, with a fall of 142 feet on this canal (Trolhätta), which is 22 miles long. The breadth of the canal-bottom is 39 feet in soil and 23 feet 5 inches in rock, with a depth at mean water-level of 12 feet 8 inches. The number of vessels passing annually is about 7000. _The West Göta Canal_, connecting the Wenner and Wetter lakes, rises from the former by a series of nineteen locks, or a height of 154 feet 6 inches, to the summit level, which is 300 feet above the sea, and the descent from here to the Baltic, _viâ_ the East Göta canal, is by thirty-nine locks. The breadth of the bottom of these canals is 46 feet 9 inches with a mean depth of 9 feet 9 inches. These two canals were completed in 1832 at a cost of 887,500_l._ The length of navigation is 116⅔ miles, of which 54⅓ miles are artificial canal, and 62⅓ miles lake channel. The traffic is from 4000 to 5000 vessels per annum.