388 Scientific Intelligence. 



tances from his generator they reappeared, to disappear again in 

 regular succession at equal intervals between his generator and 

 the wall. It is exactly the same phenomenon as what is known* 

 as Lloyd's bands in optics, which are due to the interference between 

 a direct and a reflected wave. It follows that just as Young's and 

 Fresnel's researches on the interference of light prove the undula- 

 tory theory of optics, so Hertz's experiment proves the ethereal 

 theory of electro- magnetism."— iVatare, Sept. 6, 1888, p. 446. 



J. T. 



9. Ultra violet Spectra of Metalloids. — M. Deslandres gives a 

 full history of the work of previous observers aud discusses the 

 division of the spectra into groups, particularly of the ultra violet 

 spectrum of ozone, which he believes to be composed of that of ozone 

 and oxygen. He has also verified the law that the band spectra 

 show a repetition of similar bands or series of similar lines, and 

 present an analogy to lines of metals which show a similar repe- 

 tition. He indicates a simple relation between the spectrum of 

 the vapor of water and that of oxygen, that is to say, between 

 the spectrum of a compound and one of its components. The in- 

 vestigation of the author was undertaken with apparatus of com- 

 paratively small dispersion. Plates accompany the article. — 

 Annates de chimie et de physique, Sept., 1888, pp. 1-86. J. t. 



10. A Substitute for Bisulpliide of Carbon in Optical work. — 

 H. G. Madax recommends the use of phenylthiocarbimide. Its 

 density is 1"35, boiling point 222°. Index of refraction for B and 

 G lines 1"639 and 1*707. It has the same dispersive power as 

 bisulphide of carbon, and can be used in prisms to more advan- 

 tage than the latter. — Chem. Neics, lvi, p. 257-258, 1887. J. t. 



11. Index to the Literature of the Spectroscope, by Alfred 

 Tucker man, Ph.D. Smithsojiion Miscellaneous Collections. — 

 This work contains a list of all the books and articles upon the 

 spectroscope and spectrum analysis which have been published 

 up to July, 1887. It contains a bibliography of the History; of 

 the books; of the apparatus; of the analysis in general ; of quali- 

 tative analysis ; of quantitative analysis; of absorption spectra; 

 of alkalies and alkaloids; of astronomical spectroscopy ; of carbon 

 compounds ; and of the spectra of the metals ; together with a 

 list of the authors. The number of titles which the index contains 

 is 3,829 and the number of authors 799. These numbers show 

 how great a service Mr. Tuckerman has rendered to the workers 

 in the field of spectrum analysis. The task of looking up a 

 subject upon which one is engaged is always a laborious one; es 

 pecially in a subject like spectrum analysis in which there are so 

 many investigators. Few libraries, moreover, contain all the pub- 

 lications in which scientific men of different countries publish 

 their results. One who has run from alcove to alcove and from 

 library to library will take up this index with a sigh of content- 

 ment and heartily thank the author. 



