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DRAINAGE

549

DRAKE

still waters, in which their eggs are laid. The larva lives in the water, feeding on insects and very small fish, which are caught by a peculiar claw. When ready to transform,

DRAGON-FLY

the nymph crawls out of the water on the stem of a water-plant, its outer case splits open along the back, and the perfect insect issues from it.

Drainage, the means of escape for free water of the soil, which are (i) that afforded by the slope of the land, which may carry off much of the rainfall before it can sink into the ground, and (2) that given by underground facilities. On rather level land the excess water not absorbed by the soil itself tends to sink until it meets an impervious layer, and to spread on this until it escapes through some hillside as springs. If there is no such escape, the water remains as an underground lake saturating the soil to a level more or less below the surface. This level or water-table tends to rise according to the wetness of the season, and to fall with the dryness, or proportionably to the facilities for escape by artificial drainage. If the water-table is too near the surface, the air necessary for plant-roots is excluded from the soil. This tends to make roots, as, for instance, of grains, spread out in the upper layer of earth instead of striking deep. If the district is later subjected to drouth, the plant fails of its water-supply as the water-table descends below the layer of soil occupied by the roots. Artificial drainage is accomplished (i) by open ditches or (2) by covered drains. Shallow surface-drains, made by plowing, serve to carry off only surface-water. Dug ditches may also serve as outlets for covered drains. Covered or under drains are made by placing large stones, poles, brush or tiles at the bottom of a trench and covering with soil. They are made from 25 feet apart in heavy soils to 200 feet apart in light soils, and from three to four feet deep, the depth increasing with the distance between the drains. Tiles are made of clay, burnt like brick, are hollow and more or less cylindrical. They are more lasting than wood and more cheaply laid than stones, unless the latter are in the field and have to be gotten out of the way. The benefits of under-drainage are these:

SIR  FRANCIS   DRAKE

(i) By removing the free water to a lower level, the soil occupied by capillary water (see CAPILLARITY) is deeper, and more soil is available for plant roots. (2) Soil can more readily absorb rain-water and prevent surface-wash. (3) It aids ventilation of the soil, and so aids it in warming earlier in the spring and later in the fall. (4) It allows fertilizers to be carried into the soil instead of being washed off when the land has a slope. (5) It aids in various useful chemical changes. See King, The Soil. Drainage=CanaI. See CANALS. Drake, Sir Francis, a celebrated English sailor, was born in Devonshire, probably

about 1540* though some authorities give the date of his birth as 1539. He was educated by his uncle, Sir John Hawkins, and was brought up to a sea-faring life. At 20 he made a voyage to Guinea, and two years later he was captain of the Judith in the expedition of Hawkins to Mexico. When he came back to England, he had gained a great reputation, but had lost all he had invested in the expedition. Soon after, he plundered many of the Spanish settlements in South America, and marched across the Isthmus of Panama, where, by climbing a high tree, he saw the waters of the Pacific. In 1577, under the favor of Queen Elizabeth, he set out with five vessels, intending to pass through the Straits of Magellan and explore the waters he had seen from the Isthmus of Panama. All but his own ship were separated from him by the time he had passed the straits, but he went forward alone, plundered the Spanish settlements in Chile and Peru, and claimed California in the name of his queen. He tried to find a northeast passage to the Atlantic, but was driven back by the cold. Instead of returning to England by the way he had come, he determined to make a circuit of the globe, and having crossed the Pacific and Indian Oceans and sailed around the Cape of Good Hope, he reached England in November, 1580, nearly three years after he had set out. Soon after his arrival, the queen paid him a visit, and ate dinner on board his ship, after which she made him a knight. Five years later, as war had broken out between England and Spain, Drake captured several Spanish towns in the West Indies, and two years later he entered the port of Cadiz in Spain, and destroyed a great