RECENT ADVANCES IN SCIENCE 623 



he finds their separation not markedly different in the two 

 cases and concludes that Albrecht's results are probably- 

 illusory. A similar conclusion is arrived at by Dr. T. Royds 

 (Kodaikanal Bulletin, xlviii.), who has measured directly the 

 sun-minus-arc displacements of different lines, using photo- 

 graphs of solar and arc spectra on the same plane. Com- 

 paring the sun-arc displacement with Albrecht's residuals, he 

 finds that the former are only about one-quarter as large as 

 the latter and concludes that the latter are fictitious. The 

 question has been taken up from the theoretical point of view 

 by Sir J. Larmor in the Observatory, xxxix, 191 6, p. 103, who 

 shows that very close spectrum lines ought to repel each 

 other, if they represent independent vibrations. If then 

 an iron line in the solar spectrum has a close companion 

 due to another substance, a displacement of the solar line 

 relative to the arc line may be looked for. If, however, the 

 two adjacent lines are due to the same substance, as in the 

 researches of Evershed and Royds, then no sensible difference 

 should be expected, as regards their separation, between the 

 solar and arc spectra. These results are an intrinsic property 

 of the vibrations of the source, and any effects due to anomalous 

 dispersion would be superposed on these. It seems probable, 

 therefore, that the results so far obtained cannot be regarded 

 as either establishing or refuting the theory of anomalous 

 dispersion. 



A Trans-Neptunian Planet. — In Memoirs of the Lowell 

 Observatory, vol. i. No. 1, Percival Lowell has embodied the 

 results of investigations, extending over many years, on the 

 problem of a possible trans-Neptunian planet. The investiga- 

 tion is based upon the residuals between the places of Uranus 

 obtained by observation, and those given by Leverrier's theory, 

 and Gaillot's later and more accurate theory. Adams and 

 Leverrier when searching for Neptune had residuals amounting 

 to 133" to base their investigations upon, whereas the residuals 

 of Uranus do not anywhere exceed 4"' 5. Such small residuals, 

 affected as they are by errors of observation and possible 

 errors in the theoretical positions, cannot in the nature of 

 events furnish a conclusive proof of a new planet. The 

 residuals are, however, decreased by 71 per cent, on that 

 hypothesis, so that there is a reasonable probability as to its 

 reality. The position of the planet can, however, be but vaguely 



