W. H. Wheeler— The Warp of the Hamber. 569 



and the Ouse witli the Hurnber, exteuding over a length of thirty- 

 five miles, is very highly charged with solid matter in suspension, 

 the maximum quantity being attained in the Summer, when the 

 downward flow of the fresh water is at a minimum, the quantity 

 then in suspension amounting to as much as 2,240 grains, or nearly 

 the third in a cubic foot of water. Above and below this zone the 

 quantity diminishes to 262 grains up the river Trent and 202 grains 

 near the Albert Dock at Hull, while off Spurn, at the entrance to 

 the river, there is no mud in suspension, but only a few grains 

 of clean sand. The floor of the North Sea at the entrance is covered 

 with clean sand and shells, the beach up to Grimsby also being 

 covered with sand. 



The solid matter in suspension is derived from the detritus washed 

 off the land and poured into the river when freshets occur, or from 

 the erosion of the banks of the river and its tributaries. The greater 

 quantity that prevails in the more turbid zone is due to the matex'ial 

 being kept in a state of oscillation by the ebb and flow of the tides 

 when the quantity of fresh water flowing down is not sufficient to 

 carry it out to sea. 



The average quantity of solid matter contained in thirteen other 

 English rivers when in flood is 200 grains in a cubic foot. The 

 average rainfall within the watershed of the Humber is 29 '60 inches, 

 of which 10 inches may be taken as the quantity due to such rains 

 as produce freshets. With these figures the normal total quantity 

 of solid matter placed in suspension in floods may be put at three 

 million tons in a year. A portion of this is carried out to sea 

 in heavy freshets, and the rest remains in the river in a state of 

 oscillation. 



The tendency in all rivers, whether fresh or tidal, is for material 

 to work downward under the laws of gravity. The same quantity 

 of tidal water that flows into the river has to flow out again, but 

 its capacity for transporting material downwards is reinforced by 

 the discharge of the fresh water. 



The flood current in the Humber runs at the rate of four miles 

 an hour, and its duration varies from six hours at Spurn to two and 

 a half at Goole. It may be taken, therefore, that a particle of 

 solid matter entering the Humber at Spurn Point would not be 

 carried by the flood tide more than 20 miles up the river, or 25 miles 

 below the point where the greatest amount of solid matter is held 

 in suspension. On the turn of the tide it would be carried back 

 again. Allowing for the greater time the ebb current is running 

 above the junction of the rivers as compared with the flood, the 

 material carried down on the ebb is 73 per cent, greater than that 

 carried up on the flood. 



Taking the length of the Holderness Cliffs as 34 miles, the 

 average height at 12 yards, and the mean annual loss at 2^ yards, 

 the mean quantity falling on the beach is about V^ million cubic 

 yards a year, of which about 40 per cent, consists of stones, gravel, 

 and coarse sand, leaving less than a million cubic yards to be 

 washed away. The foot of the cliffs is only reached for about four 



