284 British Association for the Advancement of Science. 
moves with a given velocity proportionate to the depth of the fluid, 
equal, in fact, to the fall of a heavy body through half the fluid. In 
some cases, the boat being stopped, Mr. Russell had followed the 
wave for a mile, and found it advance at the same rate. ‘The ob- 
ject then would be to make the centre of the vessel coincide as 
much as possible with the centre of the wave, thereby diminishing 
the anterior wave and diminishing the resistance. ‘This wave is at 
present generated to so enormous an extent, that in one case the 
waves extended to a considerable depth for a mile and a quarter, 
the depth of the river being increased one and a half foot in a chan- 
nel of five hundred yards. In six or seven feet water the immer- 
sion would be three feet more at stem than when the boat was at 
rest, the progress being doubly impeded by the anterior wave, and 
by the stern depression. ‘The question then was to what was the 
wave due? and how was it to be got rid of? In general, the greater 
the difference between the velocity of the vessel and that of the — 
wave, the more the impediment was diminished. ‘The increase of 
the velocity of the anterior wave relieves the vessel, and this is ob- 
tained, not by widening, but by deepening the channel, while at the 
same time the velocity of the stern wave is increased, so as to come 
forward to the centre of the vessel. In one instance a vessel moved 
at the rate of four miles with twenty two strokes a minute, at six 
miles with thirty five strokes, and at five and a half miles with from 
sixty to seventy strokes. The next great impediment to steam 
navigation consisted in the formation of lateral currents on the side 
of the vessel, which, having the same direction with the motion of 
the paddles, had the effect of diminishing the relative difference of 
the velocity of the paddles and of the fluid, and thus diminished the 
propelling power of the paddles, the engine being obliged to make 
an additional number of strokes. The: third evil arose from the 
stern or posterior wave or surge, by which great injury was done to 
the banks of the river, and to the smaller vessels navigating it. At 
an increased velocity this wave rises in a cycloid form into a break- 
ing surface. ‘The remedy for these evils was to be found, not in 
widening the river, as generally supposed, nor in giving gradual or 
gentle slopes to the sides of the channel, but in deepening the river 
and rendering its sides as nearly vertical as possible, by which the 
impediments were diminished to a very great amount. Mr. Russell 
had made experiments with different forms of channels, as :— 
