a. Particles with Lujlit Atoms. 561 



of force round the nucleus and rapid variations in direction 

 and magnitude of the forces for distances of the order of the 

 diameter of the electron. In our ignorance of the detailed 

 structure of the nucleus, we can only speculate as to the 

 magnitude and direction of the forces close to it. Con- 

 sidering-, however, the enormous repulsive force between two 

 positive nuclei in collision at a distance of 3xl0" 13 cin. — 

 about five kilograms weight on the inverse square law, — it is 

 to be anticipated that not only the structure of the complex 

 helium nucleus should be much deformed, but that the 

 electron itself may suffer strong deformation under the 

 intense electric forces. If such deformation of the electron 

 be possible, it is not difficult to see in a general way that the 

 forces between the nuclei in collision may vary exceedingly 

 rapidly close to the nucleus, and may even change rapidly 

 from one of repulsion to one of attraction.. It may be 

 possible in this way to explain the experimental effects 

 observed, including both the projection in the direction of 

 the a particle and the increase over the number to be 

 expected on the simple theory. 



It is of course possible to suppose that the actual law of 

 force, apart from deformation, does not follow the inverse 

 square for very small distances ; but since the inverse square 

 law appears to hold at any rate approximately for positive 

 charges up to a distance 3 x 10 ~ 12 cm., it seems simpler to 

 suppose that the rapid alteration in magnitude and direction 

 of the force close to the nucleus is due rather to a deforma- 

 tion of its structure and of its constituent parts. Taking 

 into account the intense forces brought into play in 

 such collisions, it would not be surprising if the helium 

 nucleus were to break up. No evidence of such a dis- 

 integration, however, has been observed, indicating that the 

 helium nucleus must be a very stable structure. 



It will be shown in a later paper that the anomalous 

 effects observed in hydrogen are shown also by collision of 

 swift a. particles with nitrogen and oxygen atoms and for 

 about the same distance between the nuclei. 



My thanks are due to Mr. W. Kay for his assistance in 

 counting and in all the experimental work. 



Universitv of Manchester, 

 April, 1919. 



