Question 1

How is this shipped?  What happens to the mercury if it is upside down?

Accepted Answer

ships via FedEx Ground. Barometer is mercury free. Red fluid is sealed in tube for shipping

Question 2

How the red liquid indicate pressure in millibars?  It appears to simply use the same scale as the thermometer.

Accepted Answer

A Tendency Barometer consists mainly of two parts:  A U-shaped tube (red fluid) and a thermometer (blue fluid).  The red fluid rises or falls according to changes in air pressure.  The U-shaped tube is also influenced by temperature, which is the reason why the combination with the thermometer is required.  All temperature deviations during the reading of the pressure tendency will be corrected.  All you need to do is to compare the level of the red fluid to the blue fluid.  The difference between both fluid levels (use the Celsius scale to take difference readings) is set with the pointer on the Tendency Slider, seen in your picture on the right side of the barometer case.  The changes in air pressure can be easily observed and a forecast made.

Example: When the red fluid is 6 lines below the blue fluid. -6 (remember, use the Celsius scale to take the difference) the weather forecast is for Fair Weather.  When the red fluid is 8 lines above the blue, +8, the forecast is Rainy or Stormy.

When the red and blue fluid levels are equal, the weather condition is Change. Red fluid below the blue fluid, Good Weather (high pressure).  Red fluid above the blue fluid, Bad Weather (low pressure)

You can also take actual pressure readings in hPa, which is the equivalent to millibars.  The pressure level in millibars is printed along the Tendency Slider on the right hand side of the case.  Simply turn the brass slider knob towards you to loosen it and move the slider to the proper position and retighten.  This also allows you to see the pressure change since your last observation.

Tendency Barometer Admiral Fitzroy Storm Glass Hygrometer Historical Weather Instrument

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