Porträt von Johann Jakob Hemmer

Fire safety in the Electoral PalatinateThe lightning rod

Thanks to the interests of Prince-Elector Carl Theodor von der Pfalz, the prince-elector's palaces and bastions had been protected with lightning rods since the end of the 18th century. "Hemmer's five-pointed star" provided the necessary protection. It was invented by the Jesuit priest Johann Jakob Hemmer.

Portrait of Prince-Elector Carl Theodor von der Pfalz, mid-18th century

Carl Theodor: an enlightened monarch.

A friend to the sciences

Carl Theodor was one of the enlightened monarchs of the 18th century and was a great patron of the sciences all his life. He was also interested in physical studies. In 1760, he had a physics cabinet set up in Mannheim Palace for the Jesuit priest Johann Jakob Hemmer (1733–1790). Here, Hemmer experimented with electrical charges and discharges following the example of Benjamin Franklin.

Mannheim town hall, 1840 by Joseph Maximilian Kolb

A lightning rod for all important buildings.

"Hemmer's five-pointed star"

In 1764, a lightning strike destroyed the ruins of Heidelberg Palace, and in 1769, one hit the stables at Schwetzingen. Prince-Elector Carl Theodor then followed Hemmer's advice to fit all of the palaces and bastions in the Electoral Palatinate with lightning rods. The scientist developed a "five-pointed star": a horizontal spiked cross is attached to a vertical rod. Because of the five spikes arranged like a star, the lightning rod was called "Hemmer's five-pointed star." It can be seen on the roofs of Schwetzingen Palace even today.

View of Schwetzingen Palace with lightning rod

The five-pointed star on both towers of Schwetzingen Palace.

Strange lightning rods

After the residence was moved to Munich, Hemmer equipped more palaces in Carl Theodor's territory: the old residence in Düsseldorf, Nymphenburg Palace, and, in 1783, Mannheim Palace were protected with the five-pointed lightning rod. Johann Jakob Hemmer also made other odd lightning rods: A "lightning umbrella" and a "lightning walking stick," both with long iron spikes, were intended to protect walkers from dangerous lightning strikes in stormy weather.

Visitors in front of Mannheim Baroque Palace

Mannheim Baroque Palace is one of the largest palaces in Europe.

Meteorological research

There is also a small meteorological station in Mannheim Palace. Weather conditions, wind direction, wind speed, temperature, and humidity were measured here every day. Using his own money, Carl Theodor also had 39 weather stations set up throughout Europe and recorded values at 7 a.m., 2 p.m., and 9 p.m. Mannheim local time. The "Electoral Palatinate Meteorological Society," founded in 1780, used this data to predict the weather. What's more, these three times became famous as the "Mannheim hours" and are still used today.

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