With the great impetus that soil conservation and flood-control work have given to the study of the relations of water to soil, lysimeters have received wider attention during the past decade than at any previous time. They have been used for at least two and a half centuries in studies of the percolation of water through the soil. The purpose of such studies may be strictly hydrological, attention being given only to the rate and amount of the percolate. In most of the more recent investigations the chemical composition of the percolate is analyzed, generally as a part of the study of the fertility balance of the soil, but, in some cases in connection with studies of the genesis and development of soils.