Angles of Junctions of divers. 



449 



the slope of the main stream diminishes as the water increases (see page 467).* 

 It will be seen that a near approach to uniform motion is obtained. There is 

 an exception when very hard rock is met with, and backwaters. A tributary 

 containing one-hundredth part of the water, but flowing at one hundred times 

 the slope, would enter the main river at the exact speed of the main river. 



I found, except when the shallows impeded the ships by reflecting waves 

 back from the bottom of the river, in the Rhine, the quantity of coal used, and 

 the speed attained by steamers, was uniform from near the mouth of the Rhine 

 to Mainz. (Fig. 5.) 



Fig. 10 shows the great width of a large river 1,000 miles from the sea, and' 

 decrease in width as it approaches the sea. This is the general case with large 

 navigable rivers. Directly the bar is passed a ship can sail hundreds of miles 

 in deep water. 



Fig, 11 is a cross section, a thousand miles from the sea: 



fig: 13. 



§17. 



FIG: 14.. 



The sameriirer as in JPig 13 joined 

 at right- angles to shew the 

 ijnpossibilCty of the arrangement. 



Actual junctions ofReHMiveF 

 and of her tributaries u/tth 

 Mississippi at acute angles, , 



Fig. 12 is a cross section near the Delta, proving the above law. 



Fig. 13 shows the natural junction of the tributaries of the Mississippi 

 coming in at an acute angle. 



Fig. 14 shows the imaginary junctions, supposing that in this river, the 

 branches could unite at rectangular junctions. How absurd this appears. 

 These drawings, made in 1871, are applicable to refute the theory advanced by 

 Professor Ramsay, of the Rhine having reversed its course. The angles of 

 tributary valleys are all such as would be produced by a river flowing in the 

 present direction in the Rhine valley. 



* See Note 4, page 472. 



