The DEEP WATER ISOTOPIC CURRENT ANALYZER (DWICA) was developed under a contract with William H. Johnson Laboratories, Inc. It relies on radioisotope drift time over a fixed course to measure seawater flow rates ranging from 0.002 to 10.0 knots. The device embodies 12 radiation sensors spaced equally in a circle around a radioisotope-injection nozzle. Current direction can be determined to within 15 degrees. The mass of tracer isotope injected is very small—less than 10 picograms[12] per injection—and the instrument can store enough tracer material to operate for a year. The tracer can be injected automatically at intervals from 2 to 20 minutes, depending on the current. The device sits on the sea floor, where its orientation to magnetic north can be determined within 2.5 degrees. [Illustration: _The Deep Water Isotopic Current Analyzer._] Isotope Reservoir and equipressure system Electric logic circuitry Pressure protective case Compass Sensor ring Flow baffle plate Isotope injection point [Illustration: The Deep Water Isotopic Current Analyzer.] A SEDIMENT DENSITY PROBE, developed under an AEC contract by Lane-Wells Company, employs gamma-ray absorption and backscatter properties[13] to determine the density of the sediments at the bottom of lakes, rivers, or the ocean, without the necessity of returning a sediment sample to the surface. It is expected that it can be modified to sense the water content of the sediments. These determinations are valuable not only for research, but also for activity that requires structures on the ocean floor, such as petroleum exploration and naval operations. [Illustration: _The Sediment Density Probe. The drawing shows the complete probe._] The unit consists of a rocket-like tube 26 feet long and about 4 inches in diameter, containing a gamma-ray-emitting cesium-137 source, a lead shield, and a radiation detector. The device is lowered over the side of a ship and allowed to penetrate the sediment. Once in place, the gamma ray source, shield, and detector move together up and down, inside the probe, for a distance of 11 feet, stopping every 24 inches for 4 minutes to take a measurement. Gamma rays are absorbed in any material through which they pass, according to its density. A low radiation count at the detector indicates a high-density sediment: More radiation is absorbed and less is reflected back to the detector. Conversely, a high count indicates low density. Data are recorded on special cold-resistant film. A number of different sediment measurements can be made in several locations before the unit must be returned to the surface. [Illustration: _Oxygen analyzer equipment includes the deep-sea probe (large device, center, including a special Geiger counter, the electronic assembly, a pump, and power supplies), cable for transmission of Geiger counter signals (back), and portable scaler (left)._]