Canal and river engineering: being the article "Inland navigation," from the eighth edition of the Encyclopaedia Britannica

A. and C. Black, 1858 - Nature - 165 pages

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Page 52 - A tidal bore is formed when the water is so shallow at low water that the first waves of flood tide move with a velocity so much less than that due to the succeeding part of the tidal wave, as to be overtaken by the subsequent waves, or wherever the tide rises so rapidly, and the water on the shore or in the river is so shallow that the height of the first wave of the tide is greater than the depth of the fluid at that place. Hence in deep water vessels are safe...
Page 43 - ... sometimes found to be running upwards, or in the opposite direction, at the rate of 1 to 2 miles per hour ; 6th, While the water is running downwards in the one side of the river, it is often found with an appreciable slope, and visible current running upwards on the other side of the river ; 7th, The surface of the river is therefore not a plane, but a peculiarly complicated warped surface, varying from point to point, and inclining alternately from side to side. After considering all the conflicting...
Page 122 - But there are many parts of the river where the speed of the current does not exceed 2^ miles, or even 2 miles per hour, in times of flood, and where it is, notwithstanding, more than 100 feet deep. In fact, on testing the velocity of the south-west pass, 4 miles above the bar, and in 5 fathoms water, I found the current to be but 2 miles per hour, — precisely the same as it was under like circumstances of wind and tide on the bar.
Page 52 - From the identity of this formula with that for the centre of gravity, it appears that the velocity of the great primary wave of translation of a fluid is that due to gravity acting through a height equal to the depth of the centre of gravity of the transverse section of the channel below the surface of the fluid.
Page 17 - In small works they may be made of thick planks, which are slipped into grooves formed at those narrow parts of the canal which occur under road bridges, or at contractions made at intermediate points to receive them. Self-acting stop-gates have been tried, but their success has not been such as to lead to their general introduction. Stop-gates are further found to be very useful in cases of repairs, as they admit of the water being run off from a short reach, when the repairs can be made, and the...
Page 58 - The highest tide of the year rolled up the Severn on the 1st of December. There was about 2 feet of water above the ordinary summer level in the river, and the morning was calm and favourable to the phenomenon. The stream at low water ran down at the rate of 250 feet per minute, until the bore came rolling up the river with a breast from 5 to 6 feet high at the sides, and 3 feet 6 inches in the centre. The wave was glassy...
Page 52 - The velocity of this wave in channels of uniform depth is independent of the breadth of the fluid, and equal to the velocity acquired by a heavy body falling freely by gravity through a height equal to half the depth of the fluid, reckoned from the top of the wave to the bottom of the channel. 3.
Page 129 - I tested this," says Mr. Ellet, " repeatedly, and found uniformly a column of fresh water, nearly seven feet deep, in the Gulf, entirely outside of land, and salt water at a depth of eight feet below the surface.
Page 130 - Salt water coming in slowly along the bottom, and apparently a sheet of salt water between that running out and that coming in, which will be without motion. " But as already said, and as is obvious, all the sea water that comes in must go out again. It comes in along the bottom, and it must go out between the column of salt water coming in and that of the fresh water going out. Each particle of salt water, therefore, must change its direction and position in elevation. It must pass from an inward-bound...
Page 52 - ... acquired by a heavy body falling freely by gravity through a height equal to half the depth of the fluid, reckoned from the top of the wave to the bottom of the channel. In...