IN 1929, Watson1 pointed out that very close to the surface of the Earth the atmospheric electric current, in normal fine weather field, is carried only by positive ions, so that the current density can be computed from where J is the density of the current from ionosphere to Earth, Es is the electric field at the surface, and λ+s is the conductivity of the air at the surface due to positive ions. The electric field and the conductivity, however, are measured usually at a height of approximately 1 metre. The density of the current due to conductivity, Jc(1), at this height is whereE(1) is the electric field at 1 metre and λ±(1) is the conductivity due to positive and negative ions at 1 metre. The diffusion current is usually neglected and it is assumed that the current density is approximately equal to the density of the conduction current at 1 metre, so that it can be computed from equation (2). This assumption is supported by the observations of Nolan2,3 and Hogg4. It will be shown here that this assumption is not correct and that the current density should be estimated from This statement can be proved by three arguments which will be discussed here shortly.