FLUID FLOW INDICATING AND RECORDING INSTRUMENTS; FLOW CONTROLLERS FOR AUTOMATICALLY MAINTAINING AT A PREDETERMINED GIVEN VALUE THE RATE OF FLOW OF A FLUID OR THE RATIO OF FLOWS OF FLUIDS IN SEPARATE LINES, OR THE RATIO OF SEPARATE FLOWS OF FLUID AND SOLID MATERIALS, THE APPARATUS FUNCTIONING THROUGH COORDINATION IN A RECORDING INSTRUMENT OF A SETTING OF THE PREDETERMINED VALUE AND THE AIR PRESSURE IN A GIVEN PERIOD OF TIME BASED UPON VARIATIONS OF THE FLOW RATE DURING THAT TIME; FLUID VISCOSITY INDICATING AND RECORDING INSTRUMENTS; FLUID DENSITY INDICATING AND RECORDING INSTRUMENTS; LIQUID LEVEL GAUGES [ , LABORATORY FITTINGS WITH TRANSPARENT WINDOWS FOR OBSERVATION OF FLUID FLOW IN PIPE LINES OR THE LIKE, LABORATORY GLASS PIPE AND FITTINGS AND STOP-COCKS, LABORATORY GLASSWARE, FLUID FLOW PROPORTIONERS FOR SEPARATING FLUID FLOW INTO TWO OR MORE DIFFERENT LINES IN VARIABLE RATIOS; ALARMS FOR AUTOMATICALLY SIGNALING VARIATIONS IN FLUID FLOW RATE ABOVE OR BELOW PREDETERMINED SETTINGS; ] AND PARTS AND SUB-ASSEMBLIES FOR ALL OF THE FOREGOING