361 
1921-22.] Sir Alfred Ewing’s Magnetic Atom. 
their north and south poles placed in the same way, while in the case of 
the metallic elements they are placed in the opposite way and thus ionisa- 
tion will result. 
We also have a simple explanation of why it is that if we arrange a 
chemical reaction so as to produce a voltaic current, the changes of energy 
which take place do not result in the 
local production of heat ; for, to take 
a simple example, suppose we introduce 
a zinc plate into a solution of iodine 
and zinc iodide, and suppose we imagine 
the solution to be sufficiently diluted to 
produce zinc and iodine ions, thus avoid- 
ing any controversy on this subject, we 
shall have the electrons on the outer 
shells of the two atoms swinging into 
their new position with the production 
of heat; but if we arrange the wholo 
thing as a voltaic cell with the zinc 
plate in a solution of zinc iodide and 
with a platinum plate surrounded by 
iodine, dissolved in zinc iodide, then the 
iodine atoms can be supposed to attract free electrons from the platinum 
plate which will be drawn into the outer shell, while at the same time at 
the other pole electrons are withdrawn from the zinc atom passing as free 
electrons into the zinc plate, while the zinc ion passes into solution. 
As in both cases the electrons are free, this process will take place with- 
out vibration and local production of heat, while at the same time the 
experiment can be so arranged as to make the total transformation of 
energy the same in both cases, thus supplying a source of energy for the 
external circuit. 
{Issued separately November 14 , 
