Eleetric Origin of Rigidity and Consequences. 435 
which is now the source of so much fruitful research in 
physics. It seems to me that the magnetic properties of 
metals might be the most promising field in which to test 
further the capabilities of the electric gyrostat for explaining 
the relations of matter and electricity. 
We can apply a partial check on the results of this section 
by using (12) to calculate the order of magnitude of ¢ the 
fraction of the doublets occupied at any time in the trans- 
mission of electric current. Take the case of silver, for which 
at @=273 1/y is given in the Table along with T. For the 
silver ion K is 2°66, and if we take this as a value for 
metallic Ag, then from (12) we find 7 to be of the order 
4x10-“¢. But in * The Cause of the Structure of Spectra ” 
I have shown that the fundamental period in the vibrations of 
atoms is of the order 10-™, and so @ is of the order 1/4. 
Not much weight is to be attached to this evaluation, but if 
& had come out a large integer, say 10°, there would have 
been strong reason to doubt the cogency of the preceding 
calculations. 
5. Contact Difference of Potential, and Mechanism of the 
Storage of Potential Chemical Energy in the Aither. 
The question of the contact difference of potential in metals 
is one that Lodge has kept to the fore during the last twenty 
years. It is fundamental in electricity and chemistry. The 
special point emphasized by Lodge is that the contact H.M.F. 
of metals can be calculated from their heats of combustion in 
oxygen in the following way. Conceive a gramme equivalent 
M, and M, of each of two metals to be burnt in oxygen, giving 
heat hy and h,. Let g; and gz be their electrochemical equiva- 
lents, then the quantity of electricity taking part in their 
burning is M,/g,;=M,/q.. If, then, V,—V, is the contact 
difference of potential for these two metals, the electrical 
work done by the quantity M,/g, in this change of potential 
would be (V,— Vs) M,/g;= V,Ma/g,— V2M2/g2. On equating 
this to h,—h, we get Lodge’s principle, 
: (Vi— V2) Mifgism—he - = -. ~~ (2B) 
Lodge considers that the oxygen atoms in straining at the 
metal atoms establish the contact E.M.F. If the oxygen 
could be completely got rid of, and the metals be immersed 
in perfectly dry chlorine, their contact E.M.F. ought accord- 
ing-to Lodge’s idea to be calculated from the heats of 
combination of the metals with chlorine. The evidence as a 
whole seems to me to be against this particular view, but the 
liportant matter is that the contact E.M.F. for a pair of 
2H 2 
