Scientific apparatus and instruments, namely, areometer, hydrometer [, shearometer, thermometer not for medical purposes, laboratory equipment, namely, blender and mixer for use in testing samples of oil, sand, mud, cement, water and well-fluids, electronic ph-tester; weighing apparatus and instruments, namely, pair of balances, scales, mud balances ] ; measuring apparatus and instruments, namely, pressure transmitter, pressure indicator for use on diesel engines, steam engines, gas engines, and on air compressors and pumps, indicator to measure dynamic pressures, pressure sensor for hydraulic and fuel systems of diesel engines, peak pressure meter [, downhole pressure and temperature gauges, memory gauges for pressure or temperature measurement, pressure indicator plugs for valves, viscosimeter ] ; checking in the nature of supervision apparatus and instruments, namely, dynamometer to monitor beam pumps and fluid level instruments; devices for oil, gas, diesel, air, nitrogen compression measurement; [ pressure sensors and temperature sensors for deep boreholes; ] (( sample clocks to activate electronic samplers for sampling oil, sand, mud, cement, water, well fluids )) [ ; electronic measuring apparatus, namely, sampling devices for taking samples of earth's surface or of fluids in deep holes for further laboratory analysis and identification; electrical instruments for the control of a low point of a drill string ]