12 SCIENCE PROGRESS 



approximate ellipsoids of revolution, in general larger than 

 they appear to be, especially in their equatorial regions, by 

 virtue of invisible cooler strata lying outside the visible struc- 

 ture ; the cooler, more slowly rotating strata cause reversals 

 in the spectral lines which account for many of the abnor- 

 malities. 



The last part contains determinations of the wave-lengths 

 of the nebular lines, with general observations of the spectra 

 of the gaseous nebulae, by W. H. Wright. This paper is 

 divided into three parts dealing with (i) the measurement of 

 wave-lengths and the intensities of nebular lines in 48 nebulse ; 

 (2) the study of the nebular nuclei ; (3) the investigation of 

 the distribution of nebular radiations throughout the nebulse. 

 Definitive wave-lengths of the various nebular lines are adopted 

 from the means given by nine nebulse ; many of the lines 

 were first observed in these investigations ; when known, the 

 probable origins are given. Half of the nuclei were found to 

 be of the 0-type, but the exact order of evolution remains 

 uncertain. Many interesting subjects are touched upon, in- 

 cluding a scheme, based on spectroscopic evidence, for the 

 classification of the bright-line nebulse. Lack of space 

 prevents adequate reference to these, and the reader must 

 refer to the book itself, which is well worth stud}'- by all who 

 are interested in Astronomy. 



Gravitational Astronomy. 



Banachiewicz, Th., Sur I'equation de Gauss, Pub. Ast. Obs. Univ. Dorpat, 

 24, pt. ii, 1917. 



Buchanan, D., Asymptotic Satellites near the Equilateral Triangle Equili- 

 brium Points in the Problem of Three Bodies, Trans. Camb. Phil. Soc, 

 22, 309, 1919. 



Plummer, H. C, On Professor Howe's Method of Solving Kepler's Equa- 

 tion, M.N., R.A.S., 80, 207, 1919. 



Bauschinger, J., Zur Reduction vom mittleren auf den scheinbaren Ort, 

 Ast. Nach., 210, No. 5040, 1920. 



Steenwijk, J. E. DE Vos VAN, L'Equinoxe pour 1865-0, Leiden Obs. 

 Annalen, 11, pt. iii, 1918. 



Generalised Relativity. 



SiLBERSTEiN, L., The Recent Eclipse Results and Stokes-PIanck's .^ther, 



Phil. Mag., 39, 161, 1920. 

 Majorana, Q., Sulla Gravitatione, Atti del R. Accad. dei Lincei, 28, 313, 



416, 1920. 

 HoLST, H., Die kausale Relativitatsforderung und Einstein's Relativitats- 



theorie, Det Kgl. Danske Vidensk. Selskab., Mat.-fys Meddel., 2, 11, 1919. 

 Discussion on the Theory of Relativity, M.N., R.A.S., 80, 96, 1919. 

 Larmor, Sir J., The Relativity of the Forces of Nature, M.N., R.A.S., 80, 



118, 1919. 

 DuFFiELD, W. G., The Displacement of Spectral Lines and the Equivalence 



Hypothesis, M.N., R.A.S.. 80, 262, 1920. 



