The Mind Creative NOV-Dec 2016

While photographing snowflakes was his passion, Bentley also
turned his interest to examining and sizing raindrops for seven
summers from 1898 to 1904. From that work, he gave us early
insights into raindrops and their size distribution in storms. After
some experimentation, he developed a simple yet effective
apparatus for gathering raindrops: a shallow pan of wheat flour.
At first, he simply photographed the imprints made by the falling
rain in the flour. Then in 1998, he made a serendipitous finding.
In his journal, he wrote: “In the bottom of each raindrop
impression in the flour there could always be found a roundish
granule of dough nearly exact size of raindrop. After
experimenting with artificial raindrops I could measure [its]
diameter before falling into the flour, and thus tell if the dough
granule corresponded in size with the measured raindrop.”
Over the tenure of his
raindrop studies, he
collected 344 sets of
raindrop pellets from over
70 distinct storms, including
25 thunderstorms, to which
he added meticulous
weather data about the
storm: date, time of day,
temperature, wind, cloud
type and estimated cloud
height. He concluded that
different storms produce
different size raindrops and
different size distributions.
He concluded that the size of drops and snowflakes could tell a
lot about the vertical structure of the storm.
Unfortunately, Bentley was so far ahead of his time that he
wasn’t fully appreciated by contemporary scientists. They didn’t
take this self-educated farmer seriously. It was 40 years later —
the study of cloud physics and precipitation processes would not
blossom until the 1940s — before his raindrop work was
rediscovered and and corroborated.
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