H HYDROLOGIC

INSTRUMENTS AND AUTOMATIC DEVICES FOR ENVIRONMENTAL CONTROL, NAMELY, DIGITAL PNEUMATIC FLOW-METERS, DIGITAL PNEUMATIC LIMNOMETERS, PROBES FOR MEASUREMENT OF PHYSICAL AND CHEMICAL PARAMETERS, LIQUID SAMPLE TESTERS, DIGITAL GRAPHICS RECORDERS, DIGITAL SPRAY CONCENTRATORS, EFFLUENT-METER CHANNELS, RAIN GAUGES, SNOW GAUGES, LIMNIMETERS, CURRENT METERS, FLOW-METERS, AND SELF REGISTERING TIDE GAUGES