APK1L26, 1895.] 



SCIENCE. 



475 



the period of this variable, which was 281 

 days during 1891-1S94, has changed for 

 1890. 



Eclipse of Jupiter's Fourth SateUite, February 



19,1S95: E.C.Pickering. 



A photometric observation before and 

 after eclipse, compared with the second 

 sjxtellite. 



Spectrum of Mars : Lewis E. Jewell. 



A spectroscopic study of the water vapor 

 of the earth's atmosphere shows that, unless 

 the amount of water in the atmosphere of 

 Mars is greater than that in the earth's at- 

 mosphere, it is useless to look for it there, 

 with our present instruments. The chances 

 for detecting oxygen and chlorophj'l are 

 better. 



On a Keiv Method of Mapping the Solar Cor- 

 ona : George E. Hale. 

 A method for using the diflerential bo- 

 lometer. Evidence is offered that the heat 

 radiation of the corona could be ditferen- 

 tiated from that of the adjacent sky. If one 

 member of the bolometer be exposed to a 

 portion of the sky just beyond the coronal 

 region, and the other member set success- 

 ively on tliflferent parts of the coronal image, 

 the galvanometer would indicate the vaiy- 

 ing radiation of heat intensity. Methods 

 are also proposed for reducing the galva- 

 nometer ri-adings to a form suitable for com- 

 parison with actual photogi-aphs of the 

 corona. 



On a Xew Form of Sjiectroscope : C. PuLFitiCH. 

 A translation from the Zeitschrift filr 



Instrumentenkunde, describing a modifica- 

 tion of the Littron spectroscope. 



Minor Contributions and Xotes. 



Photographic Correcting Lens for Visual Tele- 

 scopes : James E. Keeler. 



The Color ofSirius in Ancient Times: AV. T. 

 Lynn. 



On the Variability of Es.-Birm. 281: T. E. 



ESPIN. 



The Displacement of Spectral Lines Caused by 

 the notation of a Planet : James E. Keeler. 

 Br. Pulf rich's Modification of the Littrow Spec- 

 troscope. 



A list of the titles of recent publications 

 on astrophysical and allied subjects appear- 

 ing since the last numl)er is a feature of 

 each issue. 



THE physical KE\aEW, MARCH-APRIL, 1895. 



The leading article in this number of 

 the Review is one by Dr. A. S. Mackenzie, 

 On the attractions of Crystalline and Iso- 

 tropic Masses at Small Di.-itanccs The primary 

 object of the paper is to give in de- 

 tail the methods and results of an investi- 

 gation made for the purpose of determining 

 whether, within the errors of observation, 

 there is anj' deviation from the law of New- 

 ton in the case of attracting crystalline 

 matter with reference to its optic axis, and 

 the author gives also the results of some 

 experiments made with a view to testing 

 the application of the same law in the case 

 of isotropic matter at small distances. 



Physicists do not j'et fullj^ appreciate the 

 value of tlie ingenious device suggested by 

 Professor Boys through which they have 

 lately been able to use quartz fibres, which 

 furnisli a mode of suspending small masses 

 far ahead of anything before made use of 

 in stability or constancy of torsional re- 

 sistance. Like many other apparently mi- 

 nor discoveries or inventions, the introduc- 

 tion of the quart/, fiber has greatly enlarged 

 the opportunities of the experimentalist, in 

 that it provides a ready means of measur- 

 ing forces so minute as to have been thought 

 until recently quite beyond our reach. The 

 solution of problems relating to near at- 

 tractions has especially been forwarded by 

 tliis device, as Professor Boys has himself 

 shown in several able and important inves- 

 tigations. In the paper under consideration 

 Dr. Mackenzie describes the apparatus used 

 in studying the attraction of crj'stalline 



