TRANSACTIONS OF SECTION A. 569 



true corona, but at the same time it seems probable that there may be a closer 

 correspondence between pliotographs, and the eye observations which claim a large 

 ' extension ' of the corona, than has hitherto been supposed. 



21. On Pliotographs of Spiral and Elliptic Nebulce. 

 By Isaac Roberts, B.Sc, F.R.8. 



Seven photographs of spiral nebulae and four of elliptic nebuhe were exhibited 

 as lantern slides on a screen, and their forms and structures shown and described. 



The photographs were taken with a reflecting telescope of twenty inches 

 aperture and long exposures of the sensitised plates, and much additional know- 

 ledge concerning the objects was revealed by the photographs. 



The author claimed that the photographs proved the following statements: — 



1st. That the existence of spiral nebulte is a physical reality. 



2nd. That the convolutions of the spirals proceed from, or else converge to, a 

 stellar or star-like centre, and are arranged symmetrically with reference to each 

 other and to the stellar centre. 



3rd. That the convolutions, or spirals, are without exception broken up into 

 stars and star-like condensations, which are involved in nebulous matter, denser ia 

 the lines of the convolutions and fainter between them. 



The cause of the vortical motions of the nebulae was suggested to be collisions 

 between bodies in space, or else shrinkage of the diffused mass, producing concen- 

 trated gravitational effects. 



The elliptic nebulae were shown to be constituted with a stellar centre sur- 

 rounded by dense nebulosity, outside which are alternate rings of nebulosity with 

 spaces between them having little if any nebulosity in them, each nebula, as a 

 whole, presenting the appearance of a stellar system now in course of evolution 

 from a nebula of gigantic dimensions. 



By taking periodically a series of photographs and compariug them with each 

 other the changes that may take place in the nebulae will, sooner or later, be made 

 manifest. 



22. On the Formation of Soap Bubbles by the Contact of Alkaline Oleates 

 with Water. By Professor G. Quincke, F.H.S. 



This papei" was ordered by the General Committee to be j^rinted in 

 extenso. — See Reports, p. 475. 



23. On the Effect of Gases on the Surface Tension and Electrical Conduc- 

 tivity of Soap films. By H. Stansfield. 



A preliminary note was read on some experiments undertaken at the request of 

 Professor Riicker for the purpose of investigating whether the remarkably high 

 conductivity of thin soap-films found by Professors Reinold and Riicker was pro- 

 duced by the svirrounding gas. 



Experiments were also made to test whether the gas in which a film is formed 

 affected the fall in surface tension which takes place. In both cases it was found 

 that the gas was not the efficient cause of the phenomenon observed. 



24. On the Velocity of the Hydrogen Ion through Solutions of Acetates. 

 By W. C. Dampier Whetiiam, M.A. 



The velocity of the hydrogen ion in dilute aqueous solutions of ordinary mineral 

 acids was calculated by Professor F. Kohlrausch from the conductivities, and came 

 out -0030 centimetre per second when the potential gradient was one volt per 

 centimetre. Dr. Oliver Lodge measured its velocitv through chlorides, and found 

 •0029.1 



» See B.A. Rejjcnt, 1886, p. 389. 



