Abstract
The idea of an electrified atmosphere was generally accepted in Franklin's time, but the experiments of Ermann and Peltier led to the idea of a negatively charged Earth. Lord Kelvin,1 however, saw that both ideas were correct and pointed out that the electric field of the Earth is similar to that of a condenser. This analogy is not very close since only the negative plate is a conducting surface, while the positive plate is the first 8 or 10 kilometers of the atmosphere. The dielectric, moreover, which corresponds with the positive plate, is an ionized gas and for the potentials involved the “leaks” are very significant.