The rôle of the space‐charge in atmospheric electricity

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.