322 Prof. E. Taylor Jones on the Secondary 



flcation on the inner side of the surface, the electric double- 

 layer of atomic thickness, thus formed, preventing the free 

 electrons from escaping, The distribution of electric charge, 

 intensity, and potential in the double-layer is calculated and 

 the results generalized for all liquid and solid bodies. 



(2) The intrinsic potential of the atomic double-layer is 

 calculated for a few metals and shown to amount to a few 

 volts and to increase with the valency, the valent electrons 

 being the only ones effective in its production. 



(3) The contact electromotive forces of metals and di- 

 electrics are shown to be due to the difference of their 

 intrinsic potentials. 



(4) The surface-tension of liquids is accounted for by the 

 energy of their atomic electric double-layers. The atomic 

 radii and intrinsic potentials are calculated for a number of 

 metals from their surface-tension. 



(5) The intrinsic potentials thus calculated amount to a 

 few volts and permit us to arrange the metals in Volta's 

 series, while the atomic radii are very nearly equal to those 

 corresponding, on Bohr's theory, to stationary orbits of 

 second order. 



(6) The small surface-tension of dielectrics, compared 

 with metals, is explained and the surface-tension of liquid 

 hydrogen is correctly calculated by means of Debye's 

 model. 



(7) The normal stress in the double-layer is calculated 

 and its connexion with the internal pressure of liquids is 

 pointed out. 



In conclusion, I wish to express my thanks to Prof. A. 

 Yoffe for his kind interest in this work. 



Physical Institute of the Petrog-rad University, 

 December 6th, 1916. 



XXXI. The Secondary Potential of an Induction- Coil at 

 " makeT By E. Taylor Jones, D.Sc, Professor of 

 Physics in the University College of North Wales, Bangor*. 



[Plate VII. J 



ri^HE chief interest attaching to a calculation of the 

 A potential at the secondary terminals of an induction- 

 coil at "make" lies in the means which the result may 

 suggest for the reduction of this quantity. In several of the 

 processes in which induction-coil discharges are used, and 



* Communicated by the Author. 



