248 



SCIENCE 



[N. S. Vol. LIV. No. 1394 



receive a bequest estimated at from one to 

 two million dollars. 



FntE whieli resulted in damage to equip- 

 ment of approximately $20,000 and to the 

 building of about $28,000 was discovered in 

 the attic of the Richardson Chemistry Build- 

 ing, Tulane University, New Orleans, on the 

 morning of July 6. 



Dr. J. M. Bell succeeds Dr. F. P. Venable 

 as head of the department of chemistry at 

 the University of North Carolina. Dr. 

 Venable, who was formerly president of the 

 university, has resigned as head of the 

 chemistry department, but retains his pro- 

 fessorship. 



Dr. Eugene P. Deatrick has resigned as 

 instructor of soil technology. College of 

 Agriculture, Ithaca, N". T., to become associ- 

 ate professor of soils, and head of department, 

 West Virginia University, Morgantown, W. 

 Va. 



Dr. Eeuben S. Tour has been appointed 

 professor of chemical engineering at the Uni- 

 versity of Cincinnati. Dr. Tour, who suc- 

 ceeds Dr. 0. E. Sweeney, who resigned be- 

 cause of ill health, has served for several 

 years as an expert for the government on ni- 

 trate and other chemicals, and will continue 

 to act as consulting expert for the govern- 

 ment. 



Dr. Ci-ias. 0. Macklix has resigned his 

 position as associate professor of anatomy in 

 Johns Hopkins University to accept the pro- 

 fessorship of histology and embryology in 

 Western University, London, Canada. 



Professor H. Lebesqus, of the faculty of 

 sciences, University of Paris, has been elected 

 professor of mathematics at the College de 

 France. 



DISCUSSION AND CORRESPONDENCE 



SECULAR PERTURBATIONS OF THE INNER 



PLANETS 



To THE Editor of Science: It is true, as 

 Professor Poor states (Science, Vol. 54, 

 pp. 30-34, 1921), that if we are at liberty to 

 assume any distribution of density we like 

 around the sun it is not difficult to account 



for all the secular perturbations of the four 

 inner planets within their mean square errors, 

 by means of the Newtonian law of gravita- 

 tion. Professor Poor, however, does not ap- 

 pear to have read much of the paper of mine 

 to which he refers,^ or he would have noticed 

 that the density we are at liberty to assume 

 is subject to very severe limitations. It is 

 possible to estimate the density of the matter 

 at any distance from the sun directly; for the 

 amount of light it scatters is known from 

 observations of the zodiacal light and the 

 corona, and by considering different possible 

 constituents, whose scattering powers for 

 given masses are known, we can determine 

 limits to the density. Seeliger and de Sitter 

 succeeded in explaining the residual secular 

 perturbations of the four inner planets by 

 means of two ellipsoids of matter, one close 

 to the sun, and the other extending to the 

 orbit of the earth. I showed, however, in the 

 paper referred to, that the density of the mat- 

 ter between the orbits of Mercury and Mars 

 can not exceed %oo of that required by these 

 writers, and in a later paper^ I showed that 

 the disturbing effect of the matter near the 

 sun can not exceed 10"" of that supposed to 

 be produced by their inner ellipsoid. Accord- 

 ingly, none of the secular perturbations of 

 the inner planets can be explained by means 

 of the Newtonian law of gravitation. The 

 fact that the excess motion of the perihelion 

 of Mercury is accounted for by Einstein's 

 law therefore decides definitely in favor of 

 the latter. Further, Einstein's law is the 

 simplest that can account for it. None of 

 the other nine residuals exceeds 3 times the 

 corresponding mean error, and only three of 

 them the mean error itself, and there is there- 

 fore no reason to regard them as anything 

 but accidental errors. 



Harold Jeffreys 

 St. John's College, 

 Cambkidge, England 



1 ' ' The Secular Accelerations of the Four Inner 

 }Manets," Monthly Notices, E. A. S., Vol. 77, pp. 

 112-118, 1917. 



2 "On the Crucial Tests of Einstein's Theory of 

 Gravitation," loc. cit., Vol. 80, pp. 138-154, 1919. 



