There is great diversity in the length of rivers, the force of their current, and the mass and complexion of their waters; but their peculiar character is obviously dependent upon that of the country in which they are situated. As it is the property of water to follow a descent, and the greatest descent that occurs in its way, the course of a river points out generally the direction in which the land declines, and the degree of the declination determines in part the velocity of its current, for the rapidity of the stream is influenced both by its volume of water and the declivity of its channel. Hence one river often pours its tide into another without causing any perceptible enlargement of its bed, the additional waters being disposed of by the creation of a more rapid current, for large masses of water travel with a swift and powerful impetus over nearly a level surface, upon which smaller rivers would have only a languid flow. In general, the fall of the great streams is much less than what would be supposed from a glance at their currents. The rapid Rhine has only a descent of four feet in a mile between Shaffhausen and Strasburg, and of two feet between the latter place and Schenckenschauts; and the mighty Amazon, whose collision with the tide of the Atlantic is of the most tremendous description, falls but four yards in the last 700 miles of its course, or one-fourth of an inch in 1¼ mile. In one part of its channel the Seine descends one foot in a mile; the Loire, between Pouilly and Briare, one foot in 7,500, and between Briare and Orleans one foot in 13,596; the Ganges, only nine inches; and, for 400 miles from its termination, the Paraguay has but a descent of one thirty-third of an inch in the whole distance. The fall of rivers is very unequally distributed; such, for instance, as the difference of the Rhine below Cologne and above Strasburg. The greatest fall is commonly experienced at their commencement, though there are some striking exceptions to this. The whole descent of the Shannon, from its source in Loch Allen to the sea, a distance of 234 miles, is 146 feet, which is seven inches and a fraction in a mile, but it falls 97 feet in a distance of 15 miles, between Killaloe and Limerick, and occupies the remaining 219 miles in descending 49 feet. When water has once received an impulse by following a descent, the simple pressure of the particles upon each other is sufficient to keep it in motion long after its bed has lost all inclination. The chief effect of the absence of a declivity is a slower movement of the stream, and a more winding course, owing to the aqueous particles being more susceptible of divergence from their original direction by impediments in their path. Hence the tortuous character of the water-courses, chiefly arising from the streams meeting with levels after descending inclined planes, which so slackens their speed that they are easily diverted from a