LYSIMETER (a rain gauge) from two Greek words, lysis, dissolving, and metron, measure, an invention for collecting and meas uring the rain that percolates through the soil; and also for the study of the composition of drainage water. The lysimeter is a water tight box (or cylinder), enclosing a definite area to a given depth and provided with a bot tom arranged so that the percolating water that has drained through the soil may be drawn off and measured. This box is sunk into the soil to a level with its top. Sometimes the lysimeter is placed in a pit dug for.the purpose and filled with the soil removed from the pit. Usually the conditions of the soil in the lysimeter are like those of the soil outside. Lysimeters are variously made. In some cases a trench has been dug in the soil and perforated iron plates are inserted to support the mass, with a zinc funnel to collect the drainage water and con duct it to a receptacle. Although lysimeters cannot represent accurately the conditions of the natural soil, they are valuable for compara tive scientific studies on percolation, drainage and the processes of vitrification in soils. The
best work with lysimeters has been done by Stockbridge at the Agricultural College, Am herst, Mass.; Sturtevant, Babcock and Goff at the Agricultural Experiment Station, Geneva, N. Y.; and Lyon at Cornell University. In other countries the leading experimenters are: England, by Lewes, Gilbert and Warrington at Rotharnsted; France, by Dehirain at Grignon; Germany, by Gerlash at Bromberg; in Hawaii, by Eckert; and Moscow, by Klucharov. Con sult Stockbridge, 'Investigations in Rainfall, Percolation and Evaporation' (Boston 1879) ; Gilbert, 'Observations on Rainfall, Percolation and Evaporation) (in