58 



Stonar to Pegwell, and the sand-hills composed of sea-sand. 

 And from Hythe to Dungeness there are large accumulations of 

 beach and sand — the former at Hythe and Dungeness, the latter 

 at New Romney. 



Such being the state of the country under our consideration, 

 I will now proceed to discuss the question, how changes are 

 wrought in it. The great agents at work in modifying the sur- 

 face of the land are rain and rivers. Every drop of rain-water 

 that falls on the land exerts first a solution of the soil (rain- 

 water is the purest water formed naturally), and contains a 

 certain portion of carbonic acid derived from the atmosphere, 

 which renders it more powerful as a solvent of calcareous earth. 

 The water which proceeds from springs and the drainage of the 

 land is largely charged with matter in solution with carbonate of 

 lime and silicates and iron in more or less quantity. The water from 

 chalk springs generally contains from 18 to 22 grains per gallon 

 of solid residue ; while river-water contains from 22 to 29 grains 

 per gallon. The mean of these analysis would be about the 

 quantity of solid matter contained in the Stour water when quite 

 clear and free from sediment. Mr. Homersham, the engineer 

 employed by the Waterworks Company of Canterbury, calculated 

 the Stour carried on an average 20 millions of gallons per day 

 through Canterbury, and this would give a total of 3255 tons 5 

 cwt. per annum. It is then evident the river annually carries 

 away a large quantity of solid matter. This calculation does not 

 include the lesser Stour, or the numerous springs below Canter- 

 bury. Besides the quantity of solid matter thus held in solution, 

 after rain, river-water contains a very large amount of matter 

 held in suspension ; the greater the current the more this is 

 carried when a river thus charged with sediment overflows its 

 banks, the water thus spread out diminishes its velosity and, 

 consequently, carrying power — hence most of the matter held 

 in suspension is precipitated on the land on either side of the 

 river, and it annually adds to the height of the land thus flooded ; 

 — hence we find that lands that have been protected from inun- 

 dation for a great number of years are lower than surrounding 

 lands not so protected ; while, on the other hand, land frequently 

 flooded is gradually raised. A river which is embanked is pre- 

 vented from the natural relief aff"orded by the expansion of its 

 waters and deposit of its sediment, which, being thus confined 

 within a narrow channel, carries its sediment as far as the 

 velosity of its water is maintained. It must be borne in mind 

 that the greater the depth of the water, the more will be its 

 carrying powers — hence when, from any cause, it deposits its 

 sediment, it does so along its sides. Rivers empty themselves 

 into the sea ; if the waters of the latter stood at one uniform 

 height, the velocity of the water falling into it would be constant 

 with the quantity of water in the river and the amount of its 

 fall. But this is not the case ; the sea-level depends on the 

 height of its tide, which is influenced by the state of the moon 



