t 4 2 THE POPULAR SCIENCE MONTHLY 



no doubt that under favorable conditions, these particles must pass very 

 close to the nucleus and may either lead to a disruption of the nucleus 

 or to a combination with it. Unfortunately, the chance of such a dis- 

 ruption or combination is so small under experimental conditions that 

 the amount of new matter which is possible of formation within a 

 reasonable time would be exceedingly small, and so very difficult of de- 

 tection by direct methods. Very penetrating X rays or gamma rays 

 may for similar reasons prove to be possible agencies for changing 

 atoms. Although it is difficult to obtain direct evidence, I personally 

 am inclined to believe that all atoms are built up of positive electrons — 

 hydrogen nuclei — and negative electrons, and that atoms are purely 

 electrical structures. 



There can be little doubt that conditions have existed in the past 

 in which these electrons have combined to form the atoms of the ele- 

 ments, and it may be quite possible under the very intense electrical 

 disturbances which may exist in hot stars that the process of combina- 

 tion and dissociation of atoms still continues. 



In these lectures, I have tried to give an idea of some modern 

 views of the structure of the atoms and of the great variety of new and 

 powerful methods which have been applied to the attack of this problem 

 in recent years. We have seen that a heavy atom is undoubtedly a 

 complex electrical system consisting of positively and negatively 

 charged particles in rapid motion. The general evidence indicates that 

 each atom contains at its center a massive charged nucleus or core of 

 very small dimensions surrounded by a cluster of electrons probably in 

 rapid motion which extend for distances from the center very great 

 compared with the diameter of the nucleus. Such a view affords a 

 reasonable and simple explanation of many important facts obtained 

 in recent years, but so far only a beginning has been made in the attack 

 on the detailed structure of atoms — that fundamental problem which 

 lies at the basis of physics and chemistry. 



