November 2gth, 1921.] Proceedings. ix. 



metry. It is highly desirable that the work should be extended 

 to molecules of more complicated structure, but before any 

 progress can be made, it is necessary to investigate the dyna- 

 mics of collision of such molecules. 



A theorem of general application to the collision of any two 

 bodies is first established. It is found that there is a simple 

 relation between the velocity with which the points of contact 

 approach each other and the velocity with which they separate ; 

 in fact, their components resolved along the common normal 

 are shown to be the same. 



An application of this theorem to the case of diatomic mole- 

 cules leads to a simpler method of finding their motion after a 

 collision than has hitherto been used. It is found possible to 

 deduce a simple relation between the impulse, acting on each 

 body at collision, and the velocity of approach of the points of 

 contact. Now the latter is known, since the motion before 

 collision is supposed given, and hence the impulse on collision 

 is easily calculated. The velocities after collision are then 

 deduced from the ordinary dynamical equations of momentum, 

 without the elaborate analysis which previous writers have 

 indicated would be necessary. 



At a Meeting of the Council held on Tuesday, November 15th, 

 1921, the following were elected Student Associates of the 

 Society : — 



Dorothy Arning, M.A., Research Student in Physiology. The Univer- 

 sity, Manchester. Bessie Helena Edith Cadness, B.Sc, Research Student 

 in Physiology. The University, Manchester. 



General Meeting, November 29th, 1921. 

 Mr. T. A. Coward, M.Sc, F.Z.S., F.E.S. (President), in the 



Chair. 

 The following gentlemen, nominated by the Council, were 

 elected Honorary Members of the Society : — 



Professor Horace Lamb, M.A., Sc.D., LL.D., F.R.S,. lately Professor 

 of Mathematics in the Victoria University of Manchester. 65, Grange 

 Road, Cambridge. Sir Ernest Rutherford, M.A., D.Sc, LL.D., F.R.S., 

 Cavendish Professor of Experimental Physics in the University of 

 Cambridge. Neivnham Cottage, Queen's Road, Cambridge. Sir Arthur 

 Schuster, Sc.D., Ph.D., LL.D., F.R.S., F.R.A.S., Honorary Professor of 

 Physics in the Victoria University of Manchester. Ycldall, Twyford, 

 Berks. Professor G. Elliot Smith, M.A., M.D., F.R.S., Professor of 

 Anatomy in University College, London. University of London, 

 University College, .Gower Street, London, W.C.I. 



