RECENT ADVANCES IN SCIENCE 551 



ASTRONOMY. By H. Spencer- Jones, M.A., B.Sc, The Royal Observa- 

 tory, Greenwich. 



The Generalised Theory of Relativity. — At the time of writing 

 these notes, Einstein's generalised theory continues to be 

 much discussed not only in scientific periodicals, but also in 

 articles in several of the monthly reviews and in the daily 

 Press. Of the popular presentations of views for and against, 

 mention may be made of articles by Prof. Eddington in the 

 Contemporary Review for December last, and by Sir Oliver 

 Lodge, in the Nineteenth Century for December, and the Fort- 

 nightly Review for January ; also a series of three articles in 

 the Times Educational Supplement for 1920, January 22, 

 January 29, and February 5, by H. Wildon Carr, F. A. Linde- 

 mann, and A. N. Whitehead respectively. Those who require 

 an account of the theory, freed from mathematics as far as 

 that is possible, and of arguments in favour of or against 

 it, may be referred to the Monthly Notices of the R.A .S. for 

 December 191 9, in which is given in full the report of a dis- 

 cussion on the theory held at the December meeting of the 

 Royal Astronomical Society. A discussion^ on the theory was 

 also held at the meeting of the Royal Society on February 5, 

 1920, for an account of which reference should be made to the 

 Proceedings of the R.S. A study of the opening address by 

 J. H. Jeans may be particularly recommended to those inter- 

 ested. The best available summary of the mathematical 

 theory at present available in English is the " Report on the 

 Relativity Theory of Gravitation," by Prof. Eddington, pub- 

 lished for the Physical Society of London by the Fleetway 

 Press, 191 8 (price 6s. net, or in cloth, 8s. 6d.). This report 

 naturally gives an account of the theory in a very compressed 

 form, and is by no means easy reading. The Cambridge 

 University Press have announced the forthcoming publication 

 of a translation of a work by Prof. Freundlich on the " Founda- 

 tions of Einstein's Theory of Gravitation." Prof. Freundlich, 

 it may be mentioned, had proceeded to the Crimea in August 

 1 914 to test the existence of the displacement of light rays in 

 the gravitational field of the sun by taking photographs at the 

 total solar eclipse in that month. At that time, the generalised 

 theory of relativity had not been developed, and the only pos- 

 sible results anticipated were either a nil result, or the New- 

 tonian deflection of o" - 87 at the limb. The outbreak of war 

 prevented Freundlich making any observations, as he and the 

 other German observers were interned for a while by the 

 Russian Government. 



The weak point in the position of the opponents of the 

 theory, of whom Sir Oliver Lodge is the protagonist, is that 



