Predicting Weather By The Moon - Xavier University Libraries

Barometer
Pascal also missed a previous opportunity by only
two days. Had he gone up the mountain 4 days beforehand,
when he had originally planned to, and taken note of the
day and night differences in pressure at that height (which
would have entailed staying up on the mountain); then compared
them to those taken at sea-level over the same period
he might have noted some pressure discrepancy
changes over the course of a day that could be expressed
as a function of height.
The atmosphere can alter in height by several miles
twice a day like the sea tide. Yet the barometer may not
change, because it only measures, at sealevel, the weight
of a column of air a square inch in ground area. The barometer
does not and cannot measure the height of the atmosphere,
only the weight. Such an experiment has yet to be
done. I believe it has been.
Harry Alcock, an umbrella maker from the Waikato,
told me how he once fitted a filtered photographic exposure
meter to a telescope aimed at the Sun. The filter was a
lens from a discarded pair of sunglasses. The meter was
graduated for a reading range of from 14.0 – 14.7. The telescope
had an elevation angle calibration fitted, and readings
were taken throughout the day so Sun angles could be
catered for. Brightness values were recorded on every
cloud-free day. Later, the experiment was repeated using a
Cushing solar energy meter, yielding the same results. Why
brightness? Because the less compacted the atmosphere,
the duller will be the Sun, there being more interference to
the passage of the Sun’s rays through the atmospheric layers.
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