the Eartlis Magnetic Field. 89 



starts with such a scheme as the electromagnetic scheme as 

 a basis. 



Returning to the particular problem with which we are 

 here concerned, we must on this basis look upon the want of 

 symmetry, if it exists, as a perfectly regular and orderly 

 development of the electronic motions, corresponding to the 

 rotating earth, a condition of affairs originating not as a 

 mere chance for that particular sphere, but rather a type of 

 regularity common to all rotating bodies. There is nothing 

 more astonishing in the regularity of the effect, if it exists, 

 than in the similarity of constitution of all atoms of the same 

 element. When we start to attempt to explain the effect, we 

 are, however, confronted with a difficulty. It is impossible 

 for us to take cognizance of each electron in the sphere, and 

 trace by means of the electromagnetic equations the whole 

 of the phenomena associated with the production of motion 

 in the sphere. We must be content with a discussion of the 

 motions of the parts of the atom in terms of more or less 

 approximate empirical laws, involving the conception of 

 forces of a rather crude type between the electrons. These 

 laws are usually formed by analogy, after the type of the 

 laws which we find to govern the motion of matter in bulk; 

 but in apptying them to atomic dynamics we are in the 

 rather helpless condition of being unable conscientiously to 

 admit any such ideas as those of elasticity, viscosity, &c, as 

 distinct from those concepts to which the dynamical laws 

 themselves lead. We are often compelled to introduce these 

 unexplained phenomena however, but when we do dare to 

 admit them we usually feel that we ought, as a kind of 

 penance, to restrict them to the same types as those which 

 we find to hold for matter in bulk; and it is consequently 

 not surprising to find that with such a limited means of 

 attack, it is impossible to decide what the effect of motion on 

 the molecules is. In fact, the whole question resolves itself 

 into this: we have not yet sufficient experimental knowledge 

 of the constitution of the atom to be able to devise a workable 

 empirical dynamical scheme, applicable to the atom, and 

 sufficiently comprehensive to predict all those atomic pheno- 

 mena which might be imagined to be predicted by a being 

 of infinite mathematical capability, who was given the com- 

 plete electrical field of the universe at some instant, together 

 with the assumption of the electromagnetic scheme (or what- 

 ever other scheme is the correct one), to trace the course of 

 events in the universe in its future history. 



In concluding the consideration of the question of the 

 existence of the currents above referred to, it must be pointed 



