SCIENTIFIC INSTRUMENTS AND APPARATUS-NAMELY, COMBINED PIRANI AND IONIZATION GAUGES, NANOAMMETERS, HIGH RESISTANCE TEST SETS, GALVANOMETERS, AMMETERS, VOLTMETERS, THERMOCOUPLES, THERMOCOUPLE SWITCHES, THERMOCOUPLE GALVANOMETERS AND THERMOCOUPLE TEST SETS, YOUNG'S MODULUS APPARATUS, SURFACE TENSION TORSION BALANCES, THERMAL CONDUCTIVITY OF COPPER APPARATUS, CHEMICAL THERMOMETERS, TUNING FORKS, FLECTROMAGNETS, FLUXMETER AND SEARCH COILS, MAGNETIC COMPASSES, MICROSCOPES, TELESCOPES, CATHETOMETERS, GRATICULES AND RETICULES, POTENTIOMETERS AND VERNIERS THEREFOR, POTENTIAL DIVIDERS, STANDARD SHUNTS, STANDARD WESTON CELLS WITH BUILT-IN THERMOMETERS, PH METERS, MILLIVOLTMETERS, PH EXTENSION METERS, AUTOTITRATOR-CONTROLLERS, AUTOMATIC DETERMINATION OF SULFUR APPARATUS, PH ELECTRODES AND ACCESSORIES, PH AMPLIFIERS, PH ELECTRODE SELECTOR SWITCHES, CONDITION RESPONSIVE SWITCHES, DENSITY MEASURING EQUIPMENT, CONDUCTANCE BRIDGES, CONDUCTIVITY METERS AND CELLS, MILCOMETERS, CHROMATOGRAPHS AND ACCESSORIES AND COMPONENTS THEREOF, INTEGRATING AMPLIFIERS, PROCESS ANALYZERS, KATHAPOMETERS, AND STANDARD CELLS, POWER SUPPLIES, RESISTANCE BRIDGES AND BOXES, PHRECORDERS, COULOMETRIC TITRATION APPARATUS, MEGOHMMETERS, GEOPHONES, GALVANOMETER PRE-AMPLIFIERS, AND RATIO AND VOLT BOXES