498 POPULAR SCIENCE MONTHLY. 



graphs that each atom of radium which becomes iinstable throws off at 

 least as many as four alpha particles before it again reaches a condition 

 of stability, it is probable that the above lowest possible limit to the 

 life of radium, viz., 9,000 years, should be replaced by 36,000. At 

 the second or minimum rate radium would lose one-hundredth of its 

 activity in about 500 years and in 900,000 years would be no longer 

 measurably active. It appears then that within a period of a million 

 years at most all the radium now in existence will have ceased to be 

 radio-active, i. e., will have ceased to be radium. The life of uranium 

 and thorium would be from one to two million times as much, since 

 they are radiating only about a millionth as actively. 



The Transmutation of the Elements. 



The discoveries which we have attempted to describe in the pre- 

 ceding pages have seemed to lead to the startling conclusion that in 

 the case of certain elements at least, the dreams of the ancient 

 alchemists are true, for the radio-active elements all appear to be 

 slowly but spontaneously transmuting themselves into other elements. 

 The present indications seem to be that this transmutation which is 

 going on in nature is a change from the heavier atoms to the lighter 

 ones. Whether any other heavy atoms besides those of uranium, thorium 

 and radium are thus slowly disintegrating, we can not say, but probably 

 actinium must be added to the list. If any of the other known heavy 

 elements, like gold, lead, barium, bismuth, mercury, are undergoing 

 such a change, it is too slow to be detected even by the delicate test of 

 radio-activity. But it is interesting to note that the only changes of 

 this kind which have thus far been discovered to be going on among 

 the atoms are in some respects similar to the changes which are going 

 on in the organic world among the molecules. By the ordinary process 

 of decay, all organic compounds, which represent very complex molec- 

 ular structures, are continually disintegrating into simpler ones, and 

 in so doing are setting free the energy which was put into them when 

 the processes of life built them up into complex forms. Similarly, 

 the studies of the last eight years upon radiation seem to indicate that 

 in the atomic world also, at least some of the heaviest and most complex 

 atomic structures are tending to disintegrate into simpler atoms. The 

 analogy suggests the profoundly interesting question, as to whether or 

 not there is any natural process which does, among the atoms, what the 

 life process does among the molecules, i. e., which takes the simpler 

 forms and builds them up again into more complex ones. It would 

 be rash to attempt to give any positive answer to such a query, yet the 

 fact that radium now exists on the earth, taken in connection with the 

 fact that the life of radium is short in comparison with the ages in 

 which the earth has been in existence, certainly seems to point to an 

 affirmative answer. The only other alternative is to assume that 



