THE SEA-WALLER
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flats in Southampton Water. This grass spread with rapidity over mud flats extending about twenty-five miles and submerged twice a day by the ordinary tides. The grass commenced to grow in circular patches, which subsequently spread and amalgamated. In so doing it caught the detrital matter and quickly made new land. Specimens from Southampton Water were submitted to the Director of Kew Gardens, who stated that three species of Spartina occur. This grass has the advantage of being serviceable for feeding cattle, and might be used for a variety of purposes (cf. Chap. X, p. 183).
   The works commenced in the reign of Charles II for the recovery of drowned lands in the Fen District and in Lincolnshire are notable. It is stated that the Fen area is at the present time sinking at the rate of one inch per annum. There is distinct evidence of subsidence in the Island of Foulness. It is probable that the greater part of the marsh area running northwards from the estuary of the Thames is in some degree sinking, as Ordnance bench marks and level stones fixed within a marsh area are generally unreliable for levelling purposes. In order to ensure accuracy, it is necessary to carry levels back to points on stable land in rear of the marshes.
   Further instances of land reclamation in Great Britain could be multiplied. Speaking broadly, it may be said that the kingdom of Holland, comprising 13,000 square miles of some of the best agricultural land in Europe, with a population of 4| millions, has been evolved by similar operations. The Dutch system may be briefly described as follows:—
   The area to be redeemed having slowly accreted up to the stage of rough herbage, it is embanked and ditches are dug inside such banks. An accumulating reservoir is requisite to take discharge at low tide. The tract of land thus roughly cleared is, in effect, a swamp, and ditches are then driven across it so that it resembles a chess-board of land and water. The soil removed from the ditches is spread over the land to be reclaimed, and pumps are set to work to get rid of the superfluous water, the inflow of which is regulated by sluices. By this means a new polder of Dutch land comes into being.
   The art of the sea-waller is a survival, and probably has