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L. Notices respecting New Books. 



Index of Spectra. Appendix G. By W. Marshall Watts, D.Sc. t 



F.I.O. Manchester: Abel Hey wood and Son, 1896. 

 rPHE present Appendix to Dr. Watts's ' Index of Spectra ' brings 

 -*- the record of spectroscopic work down to the present time, and 

 contains results of observations published within the past three 

 years. It opens with Eowland's table of standard wave-lengths, 

 which is followed by an account of the researches of Eder and 

 Valenta. These include the spark-spectra of sodium, potassium, 

 and cadmium, and the line and band spectra of mercury. The 

 oxy hydrogen-flame spectra of several metals and oxides, observed 

 by Hartley, are next tabulated, and the record is brought to a close 

 with an account of the recent work of Eunge and Paschen on helium 

 and par-helium, the two constituents of cleveite gas. — J. L. H. 



LI. Intelligence and Miscellaneous Articles. 



ON AN ELECTROCHEMICAL ACTION OF THE RONTGEN RAYS ON 



SILVER BROMIDE. BY PROF. DR. FRANZ STREINITZ. 

 HPO Eontgen we are indebted for his great discovery of the 

 -*- property of the 47-rays of exciting fluorescence and producing 

 chemical reductions on a photographic plate. According to his 

 previous experiments, these properties are the only ones which the 

 rays have in common with those of light. Now light alters not 

 only the electromotive deportment, but also the conductivity of 

 the silver haloids. The proofs of this were furnished by 

 Becquercl and Svante Arrhenius. It can therefore scarcely be 

 doubted that electrochemical changes will be produced by the 

 Eontgen rays ; of course it is a different question whether they 

 will be accessible to observation. 



Experiments were made in both directions. In order to 

 establish the fact of a change in the conductivity, a method used 

 by Arrhenius {Wiener Berichte, vol. xcvi. p. 831, 1887) was 

 adopted. On a glass tube a silver wire was wound bifilar, 

 and then coated with ammoniacal solution of silver chloride. 

 After the ammonia and water had been evaporated, the glass tube 

 was then placed in a light-tight box, out of which the ends of 

 the wire projected. These ends were connected with a source 

 of electricity and a very sensitive galvanometer (Thorn son- 

 Carpentier). The deflexion in the galvanometer showed variations 

 when discharges were passed through a Hittorf's tube near to the 

 box. These, however, were manifestly due to inductive actions 

 on the galvanometer circuit. Eor when the induced circuit w T as 

 open, an increase in the deflexion could not with certainty be 

 established — as ought to be the case, since there was an increase 

 of the conducting power — in comparison with the deflexion 

 which was obtained before the discharge was set up. 



Experiments on the influence on electromotive behaviour were 

 attended with better success. A square platinum-foil, 2 cm. in the 

 side, was coated electrolytically with an exceedingly thin layer of 



