To illustrate this principle in terms of modern science: Add four electrons (two positive and two negative) to the hydrogen atom, and you have the element lithium; knock out of the lithium atom (composed of three positive and three negative electrons) one positive and one negative electron, and you have one atom of helium (composed of two positive and two negative electrons.) And _electrons are all alike_, except that some carry a charge of positive electrification and some a negative charge--each kind (species) of atom having an equal number of positive and negative charges, thus attaining stable equilibrium. (See Soddy, _The Interpretation of Radium_, 1922.) Until quite recently it was believed that atoms could be disrupted only by temperatures higher than those obtainable in our physical laboratories, or by bombardment by electrons and helium atoms spontaneously expelled (always with enormous velocities) from radioactive substances. But this is now known to be an erroneous assumption. It was lately discovered by P. M. Basset, engineer of the Sperry Gyroscope Company, and Dr. Louis Bell, that when carbon is brought to a temperature of 5,000° C., in an arc-light used in connection with their amazingly powerful searchlight, alpha particles (helium atoms) are liberated. Such discoveries may some day lead to the transmutation of “the baser metals into gold,” thus fulfilling the dream of the alchemists of old. Quite recently, Drs. Milliken and Bowen not only developed a method for “stripping” planetary (valence) electrons one by one from atoms, but these investigations also proved that Bohr’s (simple) theory of electron orbits--which includes the statement that the energy developed when an electron jumps from one orbit to another is exactly proportional to the frequency (or wave-length) emitted--is correct. Professor Sommerfeld’s theory explaining the cause of double lines in the spectrum of hydrogen and other elements was also verified experimentally. (See _The Scientific Monthly_, Pages 665-669, June, 1924). An atom of mercury, for example, contains 80 positive charges (electrons) on its nucleus, and 80 negative outlying electrons. Were we able to expel two of its _protons_ (positive electrons), it would instantly become the metal platinum. If a negative (“planetary”) electron were also taken from it, the mercury atom would then have lost two positive charges (electrons) and one negative; that is, one positive charge on the whole: and hence it would retain 79 positive charges on the nucleus and 79 outlying negative electrons--and thus _become gold_! Thus, one element differs from another only in the number of electrons composing its atom. And this is only a more precise statement of the essential doctrine of the ancient Greek atomists.