372 PROCEEDINGS OF THE OHIO ACADEMY OF SCIENCE. 



is the result of the emission of certain rays ; that the phenomena 

 of radioactivity are due to the effects produced by these rays. 

 These rays are of three distinct kinds, distinguished from each 

 other by the terms alpha, beta and gamma. The alpha rays 

 consist of particles having an atomic mass of 4 and bearing a 

 double unit charge of positive electricity. The beta rays have 

 a much smaller mass (calculated to be about 1-1800 of the mass 

 of the hydrogen atom) and carry a unit charge of negative elec- 

 tricity. Our conception of the gamma rays is less definite. They 

 have been regarded generally as non-material and due to some 

 peculiar vibration in the ether similar to the X-rays. 



Now what are the facts connected with the disintegration 

 of uranium? Experiments show that there is first formed a 

 definite product which is known as uranium X. This product 

 in turn disintegrates forming a second product, probably the 

 substance known as ionium, and this in turn disintegrates form- 

 ing radium. This process of disintegration continues through a 

 number of subsequent products, the final one being apparently 

 lead. In a similar way thorium is undergoing spontaneous dis- 

 integration, giving rise to a series of ])roducts. The final product 

 is unknown. From analogy one would expect it to be some 

 unknown element bearing the same relative position to thorium 

 in the periodic arrangement of the elements as lead bears to 

 uranium. Up to the present time some 30 more or less well 

 defined disintegration products have l)een described. Each of 

 these products has a definite period of average life, varying 

 from millions of years in the case of uranium itself, to a few 

 hours or even minutes in the case of one or two of the disinte- 

 gration products. 



So much for the facts. Now what are the assumptions 

 that best account for these facts. All things considered the as- 

 sumptions that have met with widest acceptance regard the 

 changes taking place in the formation of one of these products 

 from another as atomic changes. If we accept this view, each 

 of the disintegration products must be regarded as an element 

 so that up to the present date some 30 new elements have been 

 added to our list as a result of the investigations bearing on 



