RADIO-ACTIVITY
The second list is theradio-activegroup of elements,—uranium, radium, thorium, actinium,etc. These all possess their characteristic properties in varying degrees,—giving off alpha, beta and gamma rays. A certain mysterious “emanation” is also emitted by radio-active elements, but the study of these rays and their influence would take us into the realm of “physics,” and would more properly belong to a book on physics than in the present, dealing with chemistry.
One very interesting fact should, however, be mentioned in this connection, and that is the evolution of matter which has been observed, as the result of spectrum analysis. We have heard much of organic evolution, meaning the evolution of life upon our planet. It is equally true that there is an inorganic evolution, in which the gradual development of chemical elements may similarly be traced. Thus, it has been noticed that, in the hottest stars, (gaseous) the fewest chemical elements exist; in those of medium temperature (metallic), more elements are found, while in those having the lowest temperature (carbon stars) the greatest number of chemical elements are to be distinguished. This seems to prove that the higher the temperature, the fewer the elements, which in turn leads to the conclusion that all elements are perhaps ultimately ONE—as Sir William Crookes suggested many years ago. As these stars cool, more and more elements seem to be “crystallized out,” so to say,—the many being formed from the fewer. The newer researches on the constitution of matter render this idea all the more plausible.