Yale Peabody Museum of Natural History
Exhibits
Spectacle or Science? Physics in the Age of Franklin

Thunderhouse
YPM catalog no. 1.442

 

The eighteenth century is commonly known as the period of “Enlightenment.” During the Enlightenment, science became more dependent on rational thinking and experimentation. Scientific activity also became a part of the free education movement giving women and the poor an opportunity to learn. Books were expensive and not everyone could read, so public demonstrations of science became immensely popular.

Above:
A thunderhouse demonstrates the principle of a lightening rod. A spark strikes the top of the tower and travels down an insulated rod to ignite some gunpowder positioned at the bottom.

If a chain was attached to the bottom of the rod and connected externally to a piece of wood, for example, the electric current would not ignite the gunpowder. Instead the current would flow through the chain and safely away from the house.

Dancing Figures
YPM catalog nos. 1.308 and 1.310

 

Traveling magic shows or carnival performers used known scientific phenomena to entertain their audiences. Performers magically made dolls dance and cannons explode using a mysterious “electric fluid” that scientists were only just starting to understand.

Above:
These dolls are made from a light-weight material called pith, which comes from plants and trees. Pith can conduct electricity.

The dolls magically danced when they were placed between two plates, one of which was grounded so no charge could reach the dolls. When a metal plate above the dolls was positively charged the doll’s arms, legs and torso would move towards it. The cotton tassels on their hats would also stand straight up and move about towards the charge.

These dolls are a more elaborate version of another experiment that uses paper. Some natural philosophers used paper figures in the shape of the devil to heighten the seemingly “supernatural” nature of the effect. Hence why this effect is commonly called the “dancing devils.”

Left: Electrostatic Hunter
YPM catalog no. 1.441

Right: Discharge Tongs
YPM catalog no. 1.028

 

The performer had to act both as a scientist and artist to make sure the demonstration worked and that the audience was entertained. The apparatus they used had to be durable but also visually appealing, like a toy. Today, many of these devices are still called “electrostatic toys.”

Above:
The shooting hunter is a similar concept to that of the voltaic pistol. The tip of the hunter’s gun was covered in gunpowder and when a charge was applied the gunpowder ignited.

These tongs transfer a charge from an electrical source to an electrostatic toy or other apparatus. The tongs can be charged using an electro static generator. The glass on these tongs acts as an insulated handle that prevents the scientist from receiving a shock.

Benjamin Franklin
Courtesy of The Papers of Benjamin Franklin, Yale University Library.

 

Such performances inspired many 18th century scientists including Benjamin Franklin whose 300th birthday was celebrated this year. Franklin contributed to the understanding of electricity through his experiments with lightening rods and his famous kite and key experiment. More importantly, however, was Franklin’s concept that electricity had both a positive and negative charge.

Leiden Jar
YPM catalog no. 1.239

 

Scientific knowledge during the 18th century swiftly developed partly because of the increasing reliance on instruments and experimentation; Franklin himself could not bring lightening down from the sky. Eighteenth century scientific equipment, like electrostatic toys, were carefully crafted as pieces of art. Yet these objects were tough enough to perform fundamental experiments that enabled scientists like Franklin to create theories about the world.

Above:
Natural philosophers in the 18th century believed that electricity was a fluid so a jar was an obvious vessel for storing this fluid. The outsides and insides of the glass jar are coated in metallic paint which helped hold the charge. A chain passes through the lid and rests on the bottom of the jar. Electricity flows up the chain and out of the jar via the brass ball on top. Similarly, electricity can flow into the jar via the brass ball and chain.

Leiden jars can be connected together by chains to form a battery, a predecessor of the modern battery.

Electrostatic Bells
YPM catalog no. 5.548
These bells are missing the clappers that hung from a central wooden pole.

 

These objects still now convey the wondrous atmosphere of 18th century science. More importantly, these objects also depict the elevated status of science during that time by a population that demanded both education and entertainment.

Above:
Each bell is electrically grounded by being connected to the wooden base. The bells would magically ring when their metal clappers acquired a positive charge from an external source. Once the clapper struck the bell it lost its charge and fell away only to soon regain another charge and strike the bell again.

Benjamin Franklin placed two bells in his stairwell. One bell was wired to his roof top lightening rod, the other to the wall. During a lightening storm, the bells would ring and marvelous sparks would pass between them. Franklin also found that the bells would ring even when a cloud past over. It is said that Franklin’s maid was terrified of the bells because she did not know what caused them to mysteriously ring.

 


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