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. 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 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, 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


This information resource of the Maryland State Archives is presented here for fair use in the public domain. When this material is used, in whole or in part, proper citation and credit must be attributed to the Maryland State Archives. PLEASE NOTE: Rights assessment for associated source material is the responsibility of the user.


Tell Us What You Think About the Maryland State Archives Website!


[ Archives' Home Page  ||  Maryland Manual On-Line  ||  Reference & Research
||  Search the Archives   ||  Education & Outreach  ||  Archives of Maryland Online ]

Governor     General Assembly    Judiciary     Maryland.Gov

© Copyright June 10, 2002Maryland State Archives