A method was devised for observing the effect of individual falling water drops on the stability of lumps or clods of soil. The number of water drops required to destroy a lump of soil increased with reduction of soil or water temp., but decreased in a wet soil as compared with a dry one. When the size of the drop was decreased, more water drops but a smaller quantity of water were required to destroy the structure. A water-drop fall of 30 cm. and a soil lump size of 0.15 gm. were found satisfactory for the soils tested[long dash]Peorian loess subsoil and Marshall silty clay loam topsoil. More variation in the number of drops required to destroy the soil structure was encountered with Marshall topsoil than with loessal subsoil.