WWW.ASTRONOMY.COM 53aureoles described by Chevreul,
though in opposite order —
namely an enormous blue
sphere of light surrounded by
a vast orange aureole. The
volcanic skies seemed to
announce the general rule of
Neo-Impressionism: “more
opposition, more brilliance.”
One painting by Seurat
moves me each time I view it
because it recalls the f lecked
complexity of the El Chichón
sky: The Eiffel Tower, a mon-
tage of predominantly blue,
red, and yellow points of color
painted from a vantage point
that looked to the southeast
across the Seine, where suchatmospheric optical effects
would be expected.
Seurat unveiled this painting
in 1889. He began working on it
around February 1887, before
finalizing the painting in his
studio just months ahead of the
tower’s completion in 1889.
During this period, the Bishop’s
ring and other aerosol effects
were still present in the atmo-
sphere. As T.W. Backhouse
reports in a March 1889 issue of
Nature: “I am informed by Miss
E. Brown, of Cirencester, thatshe saw Bishop’s ring in full day-
time as recently as last month,
not far from 12 o’clock one day.”
Adding to the lingering
effects of the Krakatau aerosols
were aerosols injected into the
atmosphere by the 1886 erup-
tion of Mount Tarawera in
New Zealand and the 1888
eruption of Mount Bandai in
Japan. So it’s possible that
volcanic aerosols from three
different eruptions contributed
to the atmospheric effects we
see in The Eiffel Tower, whose
Pointillist style is more boldly
laid down than in any previous
work by Seurat. Furthermore,
dual powerful eruptionsin 1902 (from Mount Pelée
in Martinique and Santa
María in Guatemala) created
further atmospheric effects
until 1905, about when the
Neo-Impressionist movement
began to wane.The point of
the matter?
In the nearly 40 years since
the El Chichón eruption, I
have witnessed similar large-
scale Pointillist effects only
rarely: after the 1991 eruptionof Mount Pinatubo in the
Philippines, and once during
totality at the August 2017 total
solar eclipse in Oregon, where
the sky was affected by rippling
waves of smoke from forest fires.
I have observed a similar
effect multiple times on amicroscale with another diffrac-
tion phenomenon: the pollen
corona (about 3° in angular
extent, compared with nearly
90° in the Bishop’s ring). In one
case, I was able to photograph
the Pointillist effect in the pol-
len corona, whereby a blue aure-
ole and outer yellow and orange
rings were splintered into a
blend of juxtaposed prismatic
colors, owing to scattering
effects of the airborne particles.
Is it not reasonable, then, to
at least consider the possibilitythat the flecked complemen-
tary colors in a volcanically
infused daytime sky — which
persisted in undulations
throughout Seurat’s brief span
as an artist — influenced his
Pointillist technique?
Unfortunately, we know
little about Seurat’s methods.
He died tragically of an infec-
tion in 1891, at the age of 31.
The artist left behind little in
the way of personal letters and
diaries; he also didn’t speak
much about his technique. His
interest in color theory, how-
ever, is well documented,
including that he sought a for-
mula for the precise optical
effects of his paintings. As Jo
Kirby and colleagues explain in
an article published in a 2003
National Gallery Technical
Bulletin titled “Seurat’s
Painting Practice: Theory,
Development and Technology,”
“It is important to realise that
nothing in Seurat’s art seems to
have been unconsidered.”Seurat’s The Eiffel Tower (right) was unveiled in 1889, in time for the
World’s Fair in Paris, where the actual Eiffel Tower was also unveiled. The
author made a watercolor/pencil sketch (above) showing the daytime sky
over Hawaii in July 1982, when it was influenced by El Chichón aerosols.
PAINTING: WIKIMEDIA COMMONS/LEGION OF HONOR, SAN FRANCISCO. SKETCH: STEPHEN JAMES O’MEARA“ It is important to realise that nothing in
Seurat’s art seems to have been unconsidered.”