dfth December, ii 



Professor E. A. Letts, Ph.D., F.R.S.E., F.C.S., 

 in the Chair. 



John Brown, Esq., gave a Lecture on 

 SOAP BUBBLES. 



The lecture was illustrated by a number of experiments of soap 

 bubbles in all shapes and forms. 



Mr. Brown said — The record of men of science who have 

 devoted attention to the phenomena connected with soap 

 bubbles is a pretty large one, and includes such men as the 

 celebrated Robert Boyle (who, in 1663, examined and tried to 

 account for the colours of the bubble), Sir Isaac Newton, Hooke, 

 Young, Leidenfrost, Brewster, Draper, Sir William Thomson, 

 and many others, as well as the great French physicist Plateau, 

 whose researches have a sadly pathetic interest, since he was in 

 the midst of them attacked by a disease which deprived him of 

 sight, and it was only with " that inner eye which no calamity 

 could darken," that he continued to investigate those beautiful 

 phenomena as their colours and forms were described to him by 

 his two faithful friends and assistants, Duprez and Donny. 



The soap bubble is of interest, first, on account of the peculiari- 

 ties of its own structure, its forms, its durability, and its colour ; 

 and, secondly, as an experimental tool for the investigation of 

 other physical phenomena. The round form of a free bubble 

 is due to the interaction of the air pressure inside it and the 

 surface tension or elasticity of the liquid film. Both being 

 equal all over the surface, it can be shown how no other figure 

 could satisfy the conditions. The elasticity of the film is illus- 



