However these hypotheses may fare, the electron is a fact, and the atom is very probably a more or less stable cluster of electrons. But when we go further, and attempt to trace the evolution of the electron out of ether, we enter a region of pure theory. Some of the experts conceive the electron as a minute whirlpool or vortex in the ocean of ether; some hold that it is a centre of strain in ether; some regard ether as a densely packed mass of infinitely small grains, and think that the positive and negative corpuscles, as they seem to us, are tiny areas in which the granules are unequally distributed. Each theory has its difficulties. We do not know the origin of the electron, because we do not know the nature of ether. To some it is an elastic solid, quivering in waves at every movement of the particles; to others it is a continuous fluid, every cubic millimetre of which possesses "an energy equivalent to the output of a million-horse-power station for 40.000,000 years" (Lodge); to others it is a close-packed granular mass with a pressure of 10,000 tons per square centimetre. We must wait. It is little over ten years since the vaults were opened and physicists began to peer into the sub-material world. The lower, perhaps lowest, depth is reserved for another generation. But it may be said that the research of the last ten years has given us a glimpse of the foundations of the universe. Every theory of the electron assumes it to be some sort of nodule or disturbed area in the ether. It is sometimes described as "a particle of negative electricity" and associated with "a particle of positive electricity" in building up the atom. The phrase is misleading for those who regard electricity as a force or energy, and it gives rise to speculation as to whether "matter" has not been resolved into "force." Force or energy is not conceived by physicists as a substantial reality, like matter, but an abstract expression of certain relations of matter or electrons. In any case, the ether, whether solid or fluid or granular, remains the fundamental reality. The universe does not float IN an ocean of ether: it IS an ocean of ether. But countless myriads of minute disturbances are found in this ocean, and set it quivering with the various pulses which we classify as forces or energies. These points of disturbance cluster together in systems (atoms) of from 1000 to 250,000 members, and the atoms are pressed together until they come in the end to form massive worlds. It remains only to reduce gravitation itself, which brings the atoms together, to a strain or stress in ether, and we have a superb unity. That has not yet been done, but every theory of gravitation assumes that it is a stress in the ether corresponding to the formation of the minute disturbances which we call electrons.