DEPARTMENT OF GENERAL PHYSICS. 506 



to surround tbu plate of the electroscope completely, was interposed, discharge still 

 occurred ; but it became very slight when a thin aluminium leaf was substituted 

 for the gold or silver. Discharge occurred when the electroscope was charged 

 positively, but not negatively. The charge was appi-oximately 800 volts. 



2. As the iron arc proved unsteady, a Cooper Plewitt iiviol-glass mercury lamp 

 was substituted. The illumination was insufficient to cause discharge through 

 gold or silver leaf, but took place when the plate of the electroscope was exposed 

 to the reflections. The rate of discharge caused by plates of forty elements, metals 

 and nou-metal.s, was in the order of tlieir position in the electric series, gold, 

 iron, and manganese being notable exceptions, No discharge took place if the 

 electroscope were negatively charged. 



3. The rate of discharge was greatly increased, and this order was practically 

 the same, when the plates formed part of the electroscope ; in this case, however, it 

 was necessary to charge the electroscope negatively, and again to 800 volts. 



4. The sulphides of a number of the metals in the form of plates also caused 

 discharge, but at a much slower rate ; some iodides were also measured and 

 found to cause discharge. The order, however, is quite distinct from that of the 

 elements. 



5. The plates gave a more rapid discharge with a fresh surface : they ' tired ' 

 however, and the rate of falling ofl" presented some peculiarities. For dyad 

 metals the curve presents two obvious ' breaks; and two places of constant rate of 

 ' tiring '; for tetrad metals, four such stages were observed. 



6. A unifluid cell, containing two identical plates of copper, cadmium, or gold, 

 gives a small change of potential when one plate is illuminated by ultra-violet or 

 sunlight in a tube of uviol-glass, the other plate being kept in the dark. That 

 chemical action had occurred was obvious on examining the exposed plate. 



All these phenomena are brought into line on the hypothesis that elements and 

 compounds when illuminated discharge corpuscles. 



5. Researches on nearly Pure Ozone Gas. By Erich Ladenburg, Ph.D. 



By allowing liquid ozone to vaporise into a vacuum tube nearly pure ozone 

 gas is obtained, which has a dark-blue colour in a thickness of 30 cms. The 

 absorption spectrum of this gas from 0'22 /x to 12'2 ju was now examined, and 

 some new bands were found. There are five new bands which do not belong to 

 ozone, but always appear when the liquid ozone is allowed to vaporise. The gas 

 to which they belong- can be separated from ozone. The oxygen which was used 

 for making the ozone was developed by electrolysis of boiled potassium hydrate, 

 and was therefore as pure as possible. It seems, therefore, very probable that 

 this gas is a new modification of oxygen, and this heing the case it must be 

 of higher molecular weight than ozone, because the pressure of the gas increases 

 with the disappearance of the five bands. The determination of the specific 

 gravity of this gas has proved the truth of this opinion. 



6. Photographs of Thin Liquid Films. .5y Herbert Stansfield. 



The photographs were taken with a camera specially constructed for photo- 

 graphing the structure of plane vertical films by reflected light. ^ They were 

 arranged to show the series of abrupt changes in thickness that take place during 

 the thinning of films formed from solutions of sodium and potassium oleate. Both 

 these solutions show two black stages and three greys intermediate between the 

 coloured part of the film and the black. The photographs also showed the way 

 in which solid material separates out in the films. 



See Proc. Rvy. Soc, A, vol. Ixxvii., 190G, p. 3U. 



