Sky & Telescope - April 2024 - 30

Solar History
The corona appeared to have a breadth of half the diameter
of the Moon and " had the appearance of brilliant rays. "
Baily thought its color to be " quite white " with a " vivid and
flickering appearance, " somewhat like gaslight.
But even more remarkable were " three large protuberances
apparently emanating from the surface of the Moon, but
evidently forming a portion of the corona. " They resembled
mountains " of prodigious elevation, " their color " red, tinged
with lilac or purple " or " peach blossom. " He was so captivated
by the unexpected sight of what we now know to be
solar prominences that he forgot to note whether any brilliant
beads heralded third contact. Other European astronomers
stationed elsewhere along the path of totality, some
battling clouds, also reported seeing the corona and similar
" red flames " or " fiery red tongues. "
The arresting phenomena accompanying totality incited
astronomers on both sides of the Atlantic to ask: What
were the brilliant beads? Was the gossamer corona an
atmosphere of the Sun or the Moon? What caused the
prominences? The sightings so awakened fascination with
the physical nature and constitution of the Sun that many
astronomers vowed to chase and observe every total solar
eclipse, no matter how brief the totality, how distant the
travel, or how arduous the journey.
Eclipse Reading
With all the publicity surrounding the total solar
eclipses of 2017 and 2024, several popular books have
been published about historical eclipse expeditions.
Recent examples include Steve Ruskin, America's First
Great Eclipse: How Scientists, Tourists, and the Rocky
Mountain Eclipse of 1878 Changed Astronomy Forever
(Alpine Alchemy Press, 2017); David Baron, American
Eclipse: A Nation's Epic Race to Catch the Shadow of
the Moon and Win the Glory of the World (Liveright,
2018); and Thomas Hockey, America's First Eclipse
Chasers: Stories of Science, Planet Vulcan, Quicksand,
and the Railroad Boom (Springer Praxis, 2023).
Enduring historical classics include Samual Alfred
Mitchell's Eclipses of the Sun (Columbia University
Press, 2nd ed., 1924); Mabel Loomis Todd's two books
Total Eclipses of the Sun (Roberts Bros., 1894) and
Corona and Coronet (Houghton, Mifflin & Co., 1899);
and several chapters of Agnes M. Clerke's in-depth A
Popular History of Astronomy During the Nineteenth
Century (Adam and Charles Black, 4th edition, 1902).
But for raw astronomical adventure, there is no substitution
for reading the original 19th-century reports
of eclipse expeditions at full length, many of which -
despite their dry-sounding titles and their publication
in official scientific periodicals - describe planning,
places, mishaps, and hardships in vivid detail.
30 APRIL 2024 * SKY & TELESCOPE
The Birth of Adventure Astronomy
Astronomers' interest in the nature of the phenomena they
observed during totality came at a propitious confluence
of several important independent socio-technical developments.
First, the 19th century was a heyday of the European
and American age of exploration - of charting " terra
incognita. " That included adventurous astronomical explorers
making precision measurements of long-distance arcs of
meridians or parallels of latitude, lugging tons of equipment
across waterless deserts or through dense jungles.
Second, the 19th century was the heyday of the industrial
revolution on both sides of the Atlantic. Improved navigational
techniques along with new transportation technologies
that included transatlantic steamships and extensive
railway systems made far-off lands accessible. Third, fundamental
advances in spectroscopy allowed astronomers to
begin to understand the chemical composition of celestial
objects, including the Sun.
The result? Governments, scientific institutions, and
even individual philanthropists were willing to fund eclipse
expeditions sent halfway around the world. Making astronomical
discoveries had become a matter of high-stakes
worldwide national prestige. Small or large, Victorian solar
eclipse expeditions were a significant enterprise - some
being possibly the most advanced field expeditions of any
science. These ranged in size from those comprising a few
individuals, to undertakings that required upwards of 50
(including such helpers as carpenters, bricklayers, mule
drivers, seamen, and kitchen staff). They necessitated careful
planning and overcoming challenging logistics, especially
later in the 19th century as instrumentation grew
larger and more complex.
One to four years in advance, often via handwritten
letters sent through uncertain postal systems, an expedition
leader needed to ascertain distant local terrain and
meteorological conditions of unknown regions, as well as
the presence of plague or unfriendly inhabitants, or the
absence of adequate water or food supplies. There would of
course be instrumentation to sort out - custom optical and
photographic equipment had to be borrowed, purchased,
or built. Temporary shelters for both equipment and people
would have to be designed and constructed, then disassembled
for transportation if wood or other local resources
were unavailable at the expedition's destination. Ships or
trains had to be chartered or free passage arranged through
government officials. And somehow expedition leaders
would have to find and hire the local guides the endeavor's
success would require.
Depending on the location, the travel time could range
from weeks to months. And extra time at the destination
needed to be added to allow time for meeting local dignitaries,
finding and hiring guides, setting up camp, testing equipment,
determining precise local coordinates, and rehearsing
observing procedures to take full advantage of the precious,
fleeting moments of totality.
Sky & Telescope - April 2024

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