115 
Ordinary Meeting, January 26th, 1886. 
Professor W. C. Williamson, LL.D., F.KS., President, 
in the Chair. 
On the forces concerned in producing the Solar Diurnal 
Inequalities of Terrestrial Magnetism,” by Balfour 
Stewart, LL.D., F.R.S. 
In an article on terrestrial magnetism in the present 
edition of the EncyclopcBdia Britannica,! have endeavoured 
to show two things 
(1) That of all the various hypotheses which have been 
started with the view of explaining the solar diurnal ine- 
qualities of terrestrial magnetism, the most probable is that 
which considers these inequalities to be caused by electric 
currents in the upper regions of the earth’s atmosphere. 
(2) That in the neighbourhood of the north magnetic pole 
(judging from observationsdiscussed by Sabine), such currents 
have in all probability horizontal components flowing in 
from all sides towards that pole, so that on one side of the 
pole this component will have a direction the reverse to that 
which it has on the opposite side of the pole. 
Dr. Schuster (see Keport of Magnetical Committee of 
British Association) has deduced from this the legitimate 
inference that here we must have a vertical current or 
component of currents, inasmuch as, without this, we cannot 
imagine a series of strictly horizontal currents flowing in 
from the circumference to the centre, like the spokes of a 
wheel* 
