The Course of Instability of Elements

Abstract

URANIUM and thorium being the two amongst the old elements which are unstable, and being nearly at the end of the Periodic Table, is there any more reason to regard these as the last to remain unstable, than to regard them as the first to become unstable? If they represent the last to become unstable, we might suppose that all the other elements had passed through an unstable stage and in the course of ages to have become stable, thus throwing the greater part of the earth's history into the past, with less to come in the future. If, however, we suppose that only two elements have reached the unstable stage, all the remainder will have to come to this stage in turn, thus giving to the earth a tremendously long future as compared with that which is past.