But one of the most noticeable surprises of this description occurred in the year 1896, when Professor Roentgen made public his discovery of the X-rays; for through this discovery facts were disclosed such for instance, as the permeability of solid bodies by luminous rays and the possibility of photographic examination of bony tissues in living creatures--facts entirely incompatible with prevailing ideas and teachings. But these facts were not only intrinsically veracious but were capable of occular demonstration, beyond all possibility of doubt, and thus, as nothing could be changed or refuted, _science found itself compelled, for once, to honour the truth in its initial stage_--to receive them gracefully unto itself and adopt them in its teachings. This discovery of the X-rays was followed closely by that of the N-rays, by the two Curies, husband and wife. This further discovery was a still greater surprise to the scientific world than the former one; for by its aid was established nothing less than the inconstancy of matter. Hitherto science, dealing not with knowledge, but with opinions, had held the belief that the atom is the ultimate form of matter and that no chemical or physical force can divide it, a teaching held to be incontrovertible. First, the discovery of the X-rays had markedly disturbed this belief, and then, on the discovery of the N-rays, it soon became indubitably clear that a constant destruction is taking place within the atom, an uninterrupted throwing off of smaller particles. But it is not our task to show how one discovery after another was made. We are merely interested in knowing that, because of these discoveries, we find today in the atom--not in the radium atom alone, but in every atom as such--only a union of particles identical with one another, the so-called electrons, being but special forms of electro-magnetic forces. Professor Gruner writes as follows: "The atom is no longer the accepted, final unit of matter, but has given place to the electron. The atom is no longer an individual compact particle of matter, but an aggregate of thousands of tiny bodies. Furthermore, the atom is not indestructible; it can throw off successive electrons or groups of electrons from its numerous contents and so keep up a gradual, but veritable destruction." Professor Thomson, who won the "Nobel" prize for his work on natural science, makes these distinct assertions: "(1) The electron is nothing more than a form of electricity. (2) Each electron weighs 1/770th of a fluid atom. Of an atom, that is, which, hitherto had been regarded as the smallest individual particle. (3) A fluid atom consists of 770 electrons and is formed of electricity without any other material. (4) The atoms of other elements, besides radium, are also composed of electrons and of nothing else.