224 Scientific Intelligence. 



15. Johanniskafer Light. — In an earlier paper, H. Mtjruoka 

 stated that the light from this species of fire insect, when filtered 

 through paper or cardboard, could affect photographic plates. 

 In connection with M. Kasuya the author has re-examined the 

 phenomenon and finds that it was due to a moisture in the card- 

 board which brought out a peculiar property of the latter. This 

 moisture was communicated doubtless by the fire insects. Aqueous 

 vapor alone did not produce photographic effects. When bits of 

 the cardbjoard, however, were placed in water, a photographic 

 plate exposed to the vapor of water was sensibly blackened. 

 Various organic substances were then tried, and photographic 

 effects were produced by a large range of such substances, among 

 which were resin, coffee, camphor, tea, also oil of turpentine, 

 mercury and alcohol. It was found that zinc, cadmium and 

 magnesium act upon photographic plates, and it was noteworthy 

 that cadmium and magnesium blacken photographic plates only 

 around the boundaries of the pieces of metal. Cadmium oxide 

 exhibited an effect which cannot be ascribed to radiation or to 

 vaporization. For instance, two thick pieces of cardboard A and 

 B of the size of the to-be-covered photographic plate were per- 

 forated — A with a little square hole, B with a large one, both in 

 the middle of the plates. A was laid upon a glass plate and the 

 perforation was filled with oxide of cadmium powder. B was 

 then laid on A and on B was placed a photographic plate. It 

 was expected that the blackening would extend over the entire 

 surface of the perforation in B, for the vapor of the powder 

 could reach all points of this perforation. The darkening, how- 

 ever, was confined to a surface equal to the little square opening. 



If A and B were placed l cm apart and a copper rod was placed 

 between the openings without resting on either cardboard, there 

 was no blackening under the copper rod. This seemed like a 

 phenomenon of radiation, but radiation apparently cannot explain 

 the limitation of the blackening in the first case. — Wied. Ann., 

 No. 1, 1898, pp. 186-191. J. t. 



16. On the Occlusion of Hydrogen and Oxygen by Palla- 

 dium ; by Ludwig Mond, William Ramsay, and John Shields. 

 (Abstract of a paper read December 16, 1897, before the Royal 

 Society.) — During their investigations on the nature of the occlu- 

 sion of gases by finely divided metals, and in particular on the 

 occlusion of hydrogen and oxygen by platinum black, the authors 

 have had occasion to examine the behavior of palladium to these 



The palladium was employed in three states of aggregation, 

 viz : in the form of (a) black, (b) sponge, and (c) foil. Palladium 

 black, prepared in the same way as platinum black, contains 1*65 

 per cent of oxygen, or, taking the density of palladium black as 

 12*0, 138 volumes of oxygen. It differs from platinum black, 

 however, inasmuch as the oxygen cannot be removed in vacuo at 

 a dull red heat, and consequently had to be determined in the 

 ignited substance by passing hydrogen over it and weighing the 



