Maryland State House Dome
The Franklin Lightning Rod
Just as a central government must have checks and balances to ensure its
survival, the General Assembly stipulated that the dome on the State House
be protected from Maryland weather. The amazing force and swiftness of
lightning strikes during electrical storms raises a serious threat to buildings
of large proportions. Electric fire, as it was often referred to in the
time of the dome's construction, was a mysterious force which entertained
individual's curiosity and fear 1. The General
Assembly of Maryland attempted to protect the State House from lightning
strikes as early as 1773. Charles Wallace was ordered to place a lightning
rod of at least six feet above the original cupola to "guard the Stadt
House as far as may be against any Accident from Lightning" 2.
In a letter to Daniel St. Thomas Jenifer, Wallace commented on damage done
to the first dome of the State House at Annapolis.
"The September Storm of 1775 blew off the roof, the building unavoidably
lay open near the whole of the Winter, in consequence of which, the work
of the upper Rooms which was entirely finished, was Totally destroyed.
At another time lightning very much damaged the Dome, repairing of which
cost much expense and loss of Time" 3.
Just as Clark added an additional sixty feet to the height of the dome,
an ironmaster produced a twenty-eight foot lightning rod for the second
cupola 4. Some citizens of Annapolis questioned
the efficacy of a conductor of such magnitude. During this time, heated
scientific debate raged in Europe over whether the ends of rods should
be pointed or spherical. Noted painter, Charles Wilson Peale, consulted
with Dr. Benjamin Franklin to obtain his opinion on the safety of the rod
at the State House. Franklin had invented the lightning conductor and wrote
several treatises on the properties of lightning. In his diary entry of
July 14, 1788 Peale notes
"Went with my Brother to his Excy Doctr Franklins, my Intention was
to enquire his opinion about the efficacy of the Rods on the Stadt House
at Annapolis, the Doctr was Ill & could not be seen- we amuse ourselves
in looking [at] the Bust of Genl. Washington Paul Jones &c-then Visit
Mr. Patterson & David Rittenhouse on the same enquiry about ligh[t]ning
rods. Mr. Rittenhouse 5 being of oppinion
that if the points are good and near enough the building and the part going
into the ground so deep as to get into soft earth no danger is to be apprehended,
but if the end could be put in water of a Well it would be best." 6
Benjamin Franklin's conception of lightning conduction is vital to any
modern interpretation of the architectural significance of the State House
at Annapolis. To many members of the Royal Society in London, Benjamin
Franklin was the rebellious colonies' "dealer of rags and goosefeathers"
7.
His initial observations and experiments, linking lightning to the properties
of electricity, were largely ignored by the European scientific community.
Pragmatic use for his discovery prompted Franklin to develop the conductor.
Ignoring the critics of his discovery, the inventor wrote a friend in 1750,
"and, from what I have observed on experiments, I am of opinion that
houses, ships, and even towers and churches may be effectually secured
from the strokes of lightning by their means; for if, instead of the round
balls of wood or metal which are commonly placed on top of weathercocks,
vanes, or spindles of churches, spires, or masts, there should be a rod
or iron eight or ten feet in length, sharpened gradually to a point like
a needle, and gilt to prevent rusting, or dividing into a number of points,
the electrical fire would, I think, be drawn out of a cloud silently, before
it could come near enough to strike." 8
When lightning destroyed the dome of Sir Christopher Wren's creation, St.
Bride's Church in London, the Royal Society was prompted to reconsider
Franklin's suggestions. To protect St. Paul's Cathedral from electrical
fire, the Society appointed a committee consisting of Dr. Franklin, Dr.
Watson, Dr. Canton, Mr. Delaval and Mr. Wilson to examine the question.
Franklin's assertion, that points to elevated rods were the only protective
form of conductors, was readily adopted by Watson and Canton. Watson was
one of the leading scientists who had studied electricity in England and
Canton had invented the pith-ball electrometer and other instruments 9.
Benjamin Wilson, an electrician, disagreed vehemently. He argued that the
proposed pointed rod was dangerous because it would solicit lightning;
blunt rods attached with rounded spheres would be better forms of protection.
An incident involving the Purfleet Powder magazines convinced him of his
resolve.
After the American Revolution began, the Purfleet powder magazines were
struck by lightning. The magazines had been equipped with pointed rods
and outcry arose against Franklin. Although it was later determined that
the buildings at Purfleet were ruined simply because the conductor was
defective in certain parts and not laid deep enough into the ground, Wilson
led the society into passionate debate about the respective merits of spherical
and pointed rods. The royal court faction and conservatives of England
visualized republicanism in the construction of lightning rods designed
by a representative of the dissatisfied American colonies. King George
III sided at once with Wilson and ordered a cannon ball to be placed on
top of the conductor ordered for the royal palace at Kew 10.
Accomplished researchers attempted to decide the dispute by engaging in
a series of experiments.
In the Pantheon experiments, Benjamin Wilson arranged to create an artificial
thunderstorm to be discharged upon conductors of the two forms. Although
designed to prove Franklin wrong, the experiments showed that artificial
lightning preferred the sharper rod. While it would simply glide along
the pointed conductor, it often fell with an explosion from the ball. The
fiery political debate was not settled by the scientific experiment.
"Franklin rods were more than ever abhorred by a multitude of persons,
learned and unlearned, after the great Citizen of Philadelphia had set
his hand, on July 4, to the Declaration of Independence of the 'United
States of America,' and more than a quarter of a century had to elapse,
a new generation of men growing up, before there arose a clear and unimpassioned
view about lightning conductors" 11.Examined
in this context, the 28 foot rod attached to the dome of the State House
can be considered a powerful political statement. Its combination of republican
rebelliousness with pragmatic ingenuity has successfully protected the
State House from damage.
Introduction
The First Dome, 1769-1774
The Second
Dome, 1784-1787
The Second Dome, 1787-1792
The Second Dome's Completion, 1792-1797
Conclusion
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Copyright June 10, 2002Maryland State Archives