504 TKANSACTIONS OF SECTION A. 



gases in the hot shell combine at a certain rate, and the Hame radiates heat, and 

 comes up to a certain temperature. If the mantle causes quick combination 

 intimately among its own particles, it may be possible that the temperature there 

 may be higher than in the flame itself, so that the mantle may really be hotter 

 than the flame. I have not seen this idea put forward. It is not needed to 

 explain the phenomena, and it would be curious that all the bodies capable of 

 increasing the light of pure thoria should be coloured oxides. 



It is sometimes urged that the particles of rare earths have a special way of 

 vibrating in resonance with the particles of hot gas, and thus radiate light 

 preferably. This, again, would mean elevating heat energy to a grade higher 

 than that corresponding to the temperature, without rejection of heat at a lower 

 temperature ; a violation of the second law. 



The same reasoning holds against the theory that ceria oscillates between 

 two states of oxidation. If it did it could not supply energy by such means, 

 and therefore could not deliver energy supplied as heat at a grade higher than 

 that corresponding to the temperature of the body. 



3. The Rate of Decay of the Phosphorescence of Balmain's Paint. 

 ■By the Rev. B. J. Whiteside, S.J. 



The knowledge of the rate of decay of phosphorescence is one which is of great 

 interest in connection with the question of the form under which the energy of 

 phosphorescence is stored. 



AVith the view of helping to elucidate this question, experiments were made 

 with Balmain's paint to determine the rate at which luminosity falls off with 

 time. 



The method adopted was a modified inverse square photometer. A square of 

 the phosphorescent material was compared with a square of similarly tinted glass 

 illuminated from behind by means of an incandescent electric lamp. A plate with 

 a small hole was placed in front of the lamp to limit the source. This arrange- 

 ment was moved by means of an endless coil and wheel, so as to enable tlxe 

 observer to vary the intensity of the illumination of the matching square accord- 

 ing as the intensity of the phosphorescence diminished. 



Metallic contact-pieces were placed round the wheel, so that as it was rotated 

 a series of electric currents could be obtained. These were led to a chronograph, 

 and thus the position of the source of light at any moment recorded. 



The procedure in an experiment was first to illuminate the phosphorescent 

 material for a given time by means of an arc lamp. Then as soon as possible the 

 photometer light was brought to such a distance that the matching square looked 

 as bright as the phosphorescent material. The observer then endeavoured 

 by turning the wheel to keep the matching square of an equal brightness with the 

 phosphorescent material. A record of this was obtained from the' chronograph. 



The results obtained were found to agree with a simple hyperbolic law, 

 I = ]/(« + bt). This differs altogether from the law propounded by Becquerel from 

 theoretical grounds — namely, I = l/(« + bt)". 



It is of interest to note that the rate of recovery of over-strained solids has 

 been shown to obey a simple hyperbolic law. This fact is suggestive in connection 

 witli the well-known fact that only solid materials are capable of phosphorescing, 

 and would lead to the supposition that phosiihorescent light is only a secondary 

 effect arising in connection with the recovery of the solid from an over-strained 

 condition. 



4. Chemical and Electrical Changes induced by Ultra-violet Light. 

 By Sir William Ramsay, K.C.B., and J. F. Spencer, M.Sc, Ph.D. 



1. Light from an iron arc, falling on earth-connected plates of elements, placed 

 at an angle of 45° to the cap of an electroscope, discharges the electroscope. Even 

 when an aluminium box earthed, the top closed with a gold or silver leaf so as 



