9 Apparatus and Instruments for Weighing, Measuring, Controlling, Signalling, Monitoring, and Recording-Namely, Switching, Controlling and Regulating Instruments for Industrial Furnaces, Measuring Instruments for the Determination of Oxygen Content of Molten Steel, Large Scale Indicators, Registers, and Indicators, Compensating Systems Consisting Essentially of Servo-Apparatus and Amplifiers, Potentiometers, Electrical Compensators, Transistor Measuring Choppers, Time Pattern Controllers, Radiation Pyrometers, Surface Pyrometers, Immersion Pyrometers, Thermoelements, Resistance Thermometers, Temperature Sensors, Hygrometers and Dosage Controllers