1871.] Notices of Books. 263 



magnetic action of the earth ; first, by the action of a small 

 magnet of great power near the centre of the earth {Mayer's 

 theory, adopted by Biot and Humboldt) ; secondly, by the action 

 of two magnets within the earth (Hansteerfs theory) ; thirdly, 

 by supposing that the different kinds of magnetism are dis- 

 tributed irregularly throughout the earth (Gaus's theory). The 

 latter, which is based on very elaborate mathematical calculations, 

 is spoken of as " one of the most beautiful and the most im- 

 portant investigations that has appeared for many years in 

 physical mathematics." 



A very interesting account is given under the tenth section of 

 the magnetism of iron ships and the means of obviating its 

 effect upon their compasses. The researches of Mr. Archibald 

 Smith on this subject are here introduced, together with a 

 mathematical investigation of the effect of the ship's heeling. 



The importance and value of the series of works on mathe- 

 matical physics to which this belongs, has been so fully recognised 

 by the universities, that we need say nothing to commend it. 

 Moreover, the Astronomer- Royal — who, be it remembered, has 

 been both Lucasian Professor of Mathematics and Professor of 

 Experimental Philosophy at Cambridge — is capable of treating 

 physical subjects in a manner which is possible to few, and 

 which renders any work from his pen a valuable contribution to 

 the scientific literature of the world. 



The Sun : Ruler, Fire, Light, and Life of the Planetary System. 

 By R. A. Proctor, B.A., F.R.A.S. 8vo., 480 pp. London : 

 Longmans, Green, and Co., 1871. 



The interest which the sun possesses for us is manifold. Apart 

 from the fact that he is necessary to our life, and the source of 

 all energy — i.e., of all the work done (save tidal energy) in 

 the world ; that in fact, as Mr. Proctor has it, he is " ruler, 

 fire, light, and life of the planetary system," there is a 

 special reason why we should regard our great luminary 

 with the profoundest interest. We may remember that the 

 sun has even been the symbol of the Deity, and (the symbolism 

 being forgotten) has often been himself worshipped. Agni, the 

 god of light and fire, was placed first in the Hindu Trinity, and 

 many of the most charming hymns of the Rig Vedu Sanhita 

 are addressed to him. Then the ancient Persians introduced 

 fire as the symbol of this deity, and Mr. Palgrave, during his 

 late visit to Arabia, found in certain fastnesses traces of the old 

 Sabaean worship still remaining among the inhabitants. 



But all this was before man had asked "proud philosophy " to 

 teach him what the sun is ; and since nature has been of late 

 communicating her secrets pretty freely in this direction to some 

 well-known astronomers, and the sons of science, — Herschel 



