This complexity is, in general, very great, as is demonstrated by the examination of the luminous spectra produced by the atoms, and it is precisely because of the compensations produced between the different movements that the essential properties of matter—­the law of the conservation of inertia, for example—­are not contrary to the hypothesis.

The forces of cohesion thus would be due to the mutual attractions which occur in the electric and magnetic fields produced in the interior of bodies; and it is even conceivable that there may be produced, under the influence of these actions, a tendency to determine orientation, that is to say, that a reason can be seen why matter may be crystallised.[50]

[Footnote 50:  The reader should, however, be warned that a theory has lately been put forth which attempts to account for crystallisation on purely mechanical grounds.  See Messrs Barlow and Pope’s “Development of the Atomic Theory” in the Transactions of the Chemical Society, 1906.—­ED.]

All the experiments effected on the conductivity of gases or metals, and on the radiations of active bodies, have induced us to regard the atom as being constituted by a positively charged centre having practically the same magnitude as the atom itself, round which the electrons gravitate; and it might evidently be supposed that this positive centre itself preserves the fundamental characteristics of matter, and that it is the electrons alone which no longer possess any but electromagnetic mass.

We have but little information concerning these positive particles, though they are met with in an isolated condition, as we have seen, in the canal rays or in the X rays.[51] It has not hitherto been possible to study them so successfully as the electrons themselves; but that their magnitude causes them to produce considerable perturbations in the bodies on which they fall is manifest by the secondary emissions which complicate and mask the primitive phenomenon.  There are, however, strong reasons for thinking that these positive centres are not simple.  Thus Professor Stark attributes to them, with experiments in proof of his opinion, the emission of the spectra of the rays in Geissler tubes, and the complexity of the spectrum discloses the complexity of the centre.  Besides, certain peculiarities in the conductivity of metals cannot be explained without a supposition of this kind.  So that the atom, deprived of the cathode corpuscle, would be still liable to decomposition into elements analogous to electrons and positively charged.  Consequently nothing prevents us supposing that this centre likewise simulates inertia by its electromagnetic properties, and is but a condition localised in the ether.

[Footnote 51:  There is much reason for thinking that the canal rays do not contain positive particles alone, but are accompanied by negative electrons of slow velocity.  The X rays are thought, as has been said above, to contain neither negative nor positive particles, but to be merely pulses in the ether.—­ED.]