The works of the canal and river engineer are of the most varied, difficult, and onerous character. He has to deepen the beds of rivers, so as to secure uniform depths and absolute immunity from dangers of projecting rocks, reefs, or sandbanks. He has to divert the beds of torrential streams, and construct new channels, as has been done with the Thames, the Danube, the Tees, and many other rivers. He has to overcome the obstacles to navigation presented by cataracts like Niagara, St. Anthony’s, and other falls, by laying down a new waterway, where locks or lifts will overcome the differences of level or gradient represented by the cataracts. He has to feed artificial waterways in such a fashion that they are never short of water. He has to carry canals under mountains by tunnels, and through valleys by aqueducts. He has to raise the level of his waterways for navigation or for irrigation by barrage works, like those that are now being carried out on the Nile at Damietta and Rosetta. He has to overcome the differences of level in inland seas, as has been done by the St. Mary’s Falls and Welland Canals on the American continent. He has to join together seas that have been sundered by Nature, as in the case of the Suez, Corinth, Panama, Nicaragua, and other canals. He has to build training-walls, close passes, direct and confine currents, throw dams across minor channels, concentrate low-water flows, rectify shifting sandbars, equalise and distribute water-power, cleave through mountains (as in the case of the Culebra Col, on the line of the Panama Canal), raise rivers to the level of lakes, and lower lakes to sea-level (as in the case of the proposed Nicaraguan Canal), and to deal with many other phenomena that appear to the ordinary mind to be so many impossibilities. The engineering history of some rivers is an epitome of engineering achievements. The case of the Mississippi river, in the United States, is a notable case in point. That splendid highway, with its navigation of some 15,000 miles, and its infinite number of tributaries, each of them a noble river in itself, has been regulated, canalised, and otherwise improved at a hundred different points along its course, with results that are notable in the annals of engineering precedents. Most of our rivers, lakes, and canals have gone through the same process. It has been the work of the engineer, and that alone, which has conferred upon them the advantages possessed by our great maritime highways at the present day. The extent of that work, and the means whereby it has been accomplished, are the noblest memorial of nineteenth century science.