Using an army of probes, Professor Russ Davis, and oceanographer at the Scripps Institution of Oceanography in California, is recording details of the speed and direction of the currents that drive the oceans deep beneath the surface. By the end of the century, Davis hopes that the information form 1000 probes will allow the first detailed maps to be created. The probes, called ALACEs (Autonomous Lagrangian Circulation Explorer), are designed to sink to a depth of around 1000 metres where their density is equal to the density of the sea-water. There they begin to float around under the influence of the currents. The ALACE can be made to rise to the surface again by increasing its volume, hence decreasing its density, with the help of an ingenious battery-powered pump. At the surface, the signals from its transmitter are picked up by satellite and relayed to Professor Davis so that he can chart the probe's position to within a few hundred metres.