280 Prof. W. B. Morton on the Motion of a simple 



This scheme accounts for a number of properties of the 

 elements ; but there are a few instances of disagreement 

 which are very remarkable. Thus from the point of view 

 of the atomic constitution here proposed the element Mn 

 ought to show similar properties to the halogens, and, 

 further, there is nothing in the present scheme which can 

 explain the singular position of the inert gases. 



I think the reason for this incompleteness of the scheme 

 is that, the whole mechanism of atomic constitution is not 

 given only by the number of electrons of the rings and their 

 quant-numbers. 



The electrons as part of the atomic systems are not to be 

 regarded as independent centres of force only acting on each 

 other with ordinary repulsing forces ; but they are attached 

 to each other in some other way. 



Thus the electrons of the same ring are forced to take up 

 cjuite definite orbits, either circular or elliptic, and we may 

 also imagine a mutual connexion between the motions of the 

 various ring systems. Now it is quite possible that these 

 mutual relations may modify the properties of the atoms 

 both as regards spectra, chemical, and physical properties. 



Further, the atomic properties may greatly depend on the 

 constitution of the ring next to the surface system. 



Thus the scheme here given for the surface systems may 

 be essentially right so far as it goes ; but it does not give 

 the whole mechanism of atomic constitution. 



Physical Institute, Cliiistiania. 

 September 15, 1918. 



XXIV. JS T ote on the Motion of a simple Pendulum after 

 the String has become slack. ' By W. B. MORTON, M.A., 

 Queen's University, Belfast*. 



HPHE writers of text-books appear to lose interest in the 

 JL motion of the bob of a pendulum once the string has 

 become slack. It may be worth while to point out, for the 

 benefit of teachers of dynamics, some features of interest 

 presented by the subsequent motion, which lend themselves 

 to graphical treatment. It is very unlikely that these are 

 new ; they have probably been hit upon by others engaged 

 in the work of manufacturing examination questions, but I 

 have not found them referred to anywhere. 



"When the tension of the thread vanishes the "level of 

 no velocity" or, to use the older expression, the level of 



* Communicated by the Author. 



