In the arid region of the goldfields of Western Australia a knowledge of the conditions under which a search for water is most likely to be rewarded is of prime importance to the prospector who may find himself away from the beaten tracks. There is, in the summer, little hope of finding fresh water in the long narrow bands of goldbearing greenstone-schist that run from N.N.W. to S.S.E. through Western Australia, for both the surface and the deep-seated waters of this rock-formation are then salter than those of the sea. When unprovided with ‘condensers’ for the distillation of these waters, the prospector must therefore turn towards the neighbouring granitic areas, and search either for ‘soaks’ or for the remarkable ‘gnamma’ holes of the bare rocky ridges. The first and most reliable of these sources of fresh water—the ‘soaks’ —presents nothing abnormal and requires little description. They are found in the sandy hollows at the foot of granite slopes. A well is sunk in the sand, and the water is baled as it slowly percolates into the bottom of the hole. The supply may vary from a mere trickle to several hundred gallons in twenty-four hours, according to the catchment, to the season, and to the permeability of the sand that has protected the water from evaporation since it was collected in the rock-hollow.