Happy Dalibard Day! Yes, it might not be marked as such on your calendar, but May 10 is a pretty important date in not only the history of atmospheric sciences, but also in the American struggle for independence from the British.
Not that anyone realized this at the time, mind you, but looking back with a butterfly effect-tuned mind, we're now able to appreciate the impact of one random French naturalist, an insulated iron rod and a thundercloud.
Step 1: Benjamin Franklin lays out plans for his "sentry box" experiment in a widely circulated 1751 pamphlet titled "Experiments and Observations on Electricity." The pitch was to determine whether thunderclouds were electrical by erecting a 43-foot (13-meter) iron rod, sheltering the rod's base to keep the rain off and having a volunteer attempt to draw sparks from the rod and store them in a Leyden jar.*
Step 2: The following year, on May 10, 1752, French scientist and naturalist Thomas-François Dalibard decided to test the sentry box experiment out. Which is to say he convinced a retired soldier to actually venture beneath the iron rod as a thundercloud passed over the town of Marly-la-Ville. The result? It worked! As atmospheric research and the mystery of electricity was quite the fad at the time, news of the success of this experiment spread throughout Europe. The sentry box experiment proved that clouds were electrified objects, and lightning was more than just a fashion accessory in the hands of an angry god.
Step 3: As the experiment was Benjamin Franklin's brainchild, the almanac and bifocal enthusiast became an overnight sensation. He'd (supposedly) conduct his famous kite experiment himself the following month, but the Dalibard experiment gained all the fame in Europe. Just two weeks after the events at Marly-la-Ville, Franklin's name was praised at the Royal Society of London. Franklin was awarded honorary degrees and became DOCTOR Benjamin Franklin.
Step 4: Fast-forward to November 1776 and you find Franklin arriving in France to seek aid for the upstart USA in its war against the British Empire. Franklin was a true celebrity by this point, and his work on electricity had called attention to writings on such topics as philosophy and politics. In short, European intellectuals viewed Franklin as one of their own and welcomed him into their courts with open arms. French assistance would play a crucial role in the struggle for U.S. independence.
So there you have it. University of Arizona's E. Philip Krider lays out this entire string of historic events in "Benjamin Franklin and Lighting Rods," published in the January 2006 issue of Physics today -- which you can find here.
* Devised in 1746, this was a glass jar or bottle with an outer and inner metal coating, as well as an internal brass rod. These were used in electrical experiments to store a charge. You can see some examples right here.