IV 
CONTENTS. 
No. page 
XVI. On the Faraday-Tube Theory of Electro-Magnetism. By 
the late William Gordon Brown. Communicated by 
Dr C. G. Knott, F.R.S., General Secretary, along with 
a Biographical Note of the Author, .... 225 
{Issued separately July 6, 1922.) 
XVII. The Quantum Theory of the Secondary Spectrum of Hydrogen. 
By John Marshall, M.A., D.Sc., University College, 
Swansea, ......... 247 
{Issued separately July 6, 1922.) 
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