This chapter deals with the electricity in the C, which can be investigated directly, and afterwards with the upper atmosphere, which is out of human reach, and which explored by indirect means. A method used to isolate a portion of the ground and measure the charge on it, but that most commonly used is to calculate the magnitude of the charge by the electric force it exerts in the immediate neighbourhood of the ground. Many years ago a theory was put forward by Birkeland to explain the nature of auroral displays and magnetic storms, and to explain why these phenomena are most intense in high latitudes near the poles. The atmosphere above the ground possesses in fine weather a resultant positive charge, although there are really present elementary electric particles. Professor C. T. R. Wilson theory is that thunderstorms are responsible for the maintenance of the earth's negative charge in spite of the dissipative influence of the air-to-earth current.