Optical wedges are used extensively in research for measuring and comparThey also are valuable tools for calibrating ing the brilliance of light sources. the sensitivity of photographic film. New Automatic Pipetting System.-A new device, which automatically dispenses controlled volumes of sterile liquids or chemical solutions at predetermined intervals with extreme%accuracy, has been announced by Central Scientific Co., of Chicago. Called the Maisch Automatic Pipetting System, it consists of a motorized, stainless steel metering pump, an automatic recycling timer, and a pipette control unit. This completely automatic unit facilitates dispensing of serums, pharmaceuticals, reagents or other industrial solutions that may be required in laboratory or process control. It is ideal for filling ampules with biological fluids. The Maisch pipette unit responds instantlv to split-second control of any precision timing switch having adjustable ON and OFF cycle controls. The instant a desired volume of liquid has been dispensed, the pipette control automatically recirculates the flow from the metering pump back into the pump intake, maintaining an average accuracy of 0.5 to 1 per cent for the volumes being dispensed. Any of the various Maisch metering pumps supply a continuously uniform and non-pulsating flow of liquid which is a “must” for accurate dispensing. The amount of fluid dispensed during each cycle is determined by the speed and capacity of the pump selected, the operating head pressure and time interval to which the pipette control is set. Thus, a pump dispensing at the rate of 20 ml. per sec. under any given head pressure will deliver 100 ml. when the timer is set for 5 sec. The motorized transmission units for this system are available with fixed speeds for output capacities from 11 to 150 ml. per sec.; also with governorcontrolled variable speed universal motors for adjustable output capacities from 3.4 to 30 ml. per sec., and variable speed transmissions for adjustable capacities from 0 to 150 ml. per sec. Maisch Stainless Steel Pump Heads with oilless bearings feature a positive displacement gear type construction. The newly developed quick demountable heads are interchangeable on all standard Maisch transmissions. They are sterilizable by steam autoclaving for dispensing biologicals and other sterile solutions with a uniform non-pulsating flow. Output capacities from 0 to 150 ml. per sec. The automatic recycling timer is equipped with adjustable controls for regulating on and o$ pump dispensing cycles through the Maisch pipette control unit. This provides a completely automatic time control through practically any required cycle with split-second accuracy. Single cycle timers are also available for control of dispensing cycles only. The Maisch Pipette Control Unit automatically recirculates the liquid back through the pump the instant a required volume has been dispensed into the receptacle. It is equipped with an electric solenoid and rubber tube pinch valve arrangement which shuts off or releases the flow. It is designed for continuous operation under full load with 110/115-volt, 60-cycle a-c. power. Voice-Operated Telephone.-An electronic telephone device which can understand and intelligently react to spoken numbers has been built at Bell Telephone Laboratories, research and development organization of the Bell System.