The Thunder House
In the late 1770s there was heated debate regarding the relative merits of a point or ball as the electrode of a lightning rod. Benjamin Franklin (the inventor of the lightning rod) supported the idea that the rod should terminate in a point. Others (primarily in England, where Franklin wasn’t well liked due to his support of American independence) believed a ball would make a better spark gap. After all, most of the devices up to this time used a brass ball as an electrode, Franklin’s “point” being a relatively new idea.
Dr. James Lind of Edinburgh invented the Thunder House in order to test Franklin’s theory. Experiments with the device indicated that Franklin was wrong and the ball worked better, but in truth the apparatus proved nothing. On the enormous scale of nature there is little difference between the two.
Dr. James Lind of Edinburgh invented the Thunder House in order to test Franklin’s theory. Experiments with the device indicated that Franklin was wrong and the ball worked better, but in truth the apparatus proved nothing. On the enormous scale of nature there is little difference between the two.
How does it work?
Prior to the demonstration the operator places a small bit of explosive powder in the “exploding window.” The Leyden jar is then charged to provide the energy for the “lightning”, in this case a simple spark. Using the glass ball as a handle, the operator rotates the shorting bar until a spark jumps from the jar’s electrode to the lightning rod. If the lightning rod’s ground connection is intact, the charge bleeds harmlessly away. However, if the ground is not intact, the spark ignites the powder and the window is blown away.
Prior to the demonstration the operator places a small bit of explosive powder in the “exploding window.” The Leyden jar is then charged to provide the energy for the “lightning”, in this case a simple spark. Using the glass ball as a handle, the operator rotates the shorting bar until a spark jumps from the jar’s electrode to the lightning rod. If the lightning rod’s ground connection is intact, the charge bleeds harmlessly away. However, if the ground is not intact, the spark ignites the powder and the window is blown away.