But even this is not all that can be said as to the fluctuating character of that fundamental material quality "inertia." It appears possible, if electrons approach too near each other, so as to encroach on each other's magnetic field as they move, that then their inertia may fall in value during the time they are contiguous. No experimental fact has yet suggested this at present: it is improbable that even in the tightest combinations they ever really approach close enough to each other to make the effect appreciable in the slightest degree; still, strictly speaking, the inertia of matter is a known mathematical function of the distance of electrons apart, compared with their size, as well as of their absolute speed through the ether; and hence it may be found to vary from either of two distinct reasons. Nevertheless, even this variation would not be expressed as a failure in the conservation of matter, though there is now no single material property that can be specified as really and genuinely constant. So long as the electric centres of strain, or whatever they are—so long as the electric charges themselves—continue unaltered, we should prefer to say that at least the _basis_ of matter was fundamentally conserved. Further than this, however, we cannot go; and to say, as Professor Haeckel says, that the modern physicist has grown so accustomed to the conservation of matter that he is unable to conceive the contrary, is simply untrue. Whatever may be the case in real fact, there is no question with respect to the possibility of conception. The electrons themselves must be explained somehow; and the only surmise which at present holds the field is that they are knots or twists or vortices, or some sort of either static or kinetic modification, of the ether of space—a small bit partitioned off from the rest and individualised by reason of this identifying peculiarity. It may be that these knots cannot be untied, these twists undone, these vortices broken up; it may be that neither artificially nor spontaneously are they ever in the slightest degree changed. It may be so, but we do not know; and it is quite easy to conceive them broken up, the identity of the electron lost, its substance resolved into the original ether, without parts or individual properties. If this happened, within our ken, we should have to confess that the properties of matter were gone, and that hence everything that could by any stretch of language be called "matter" was destroyed, since no identifying property remained. The discovery of such an event may lie in the science of the future; it would be an epoch-making event in the history of science, but no physicist would be upset by it—perhaps not even surprised; nor would any one have good reason to be astonished if the correlative phenomenon occurred, and under certain conditions some knots or strains were some day caused in the ether, which had not been previously there; and so "matter," or the