January 7, 1909 J 



NA TURE 



IJC) 



attitudfs of rest in British moths, predaceous insects 

 and their prey. A subject like the last, for instance, 

 worked out by the cooperation of many naturalists, 

 commends itself as zoological work of the soundest 

 sort; it brings together a mass of trustworthy in- 

 formation in regard to insect natural history, it has 

 an obvious bearing on the theory of selection, and it 

 makes towards supplying a trustworthy basis for 

 practical measures. Three of these interesting 

 bionomical memoirs are contributed by Dr. F. A. 

 Dtxev, two by the Hope professor, and one each by 

 .Messrs. T. R. Bell, A. H. Hamm, S. L. Hinde, W. J. 

 Kaye, and S. A. Neave. Three papers by Dr. Long- 

 stafi' contain records of observations — chiefly biononiic 

 — on. insects met with in various parts of the world. 

 Then follow papers, chiefly of a systematic nature, on 

 Hlattidas by Mr. R. Shelford, on " grasshoppers " by 

 Dr. J. L. Hancock, on beetles by Commander J. J. 

 Walker, .\fter these the volume ends, as it began, 

 with bionomical inquiry, from which modern ento- 

 mologists are seldom far away. We cannot look over 

 a volume like this (reviving our recollections, in some 

 cases, of papers wc had read before) without feeling 

 afresh that the entomologist, more, perhaps, than 

 most naturalists, has his finger on the pulse of evolu- 

 tion. The Hope Reports show that he is not unaware 

 of his great opportunities. 



Calcid graphiquc et nomographic. By M. d'Ocagne. 



Pp. .\xvi + 3g2-l-xii. (Paris: Octave Dion, igo8.) 



Price 5 francs. 

 The " Encyclopedic scientifique " of which this book 

 forms one volume is intended ultimately to consist of 

 1000 -volumes divided into 40 sections, written by 

 specialists in different sciences, and edited by Dr. 

 Toulouse. While aiming at the completeness of an 

 encyclopaedia, it differs from most publications bearing 

 that name in that it consists of small volumes, each 

 treating of one subject, instead of bulky volumes, each 

 containing a number of widely diverse articles. 



In this volume M. d'Ocagne deals with graphical 

 methods of computation, a subject in the development 

 of which he has himself played an important part. It 

 is pointed out that such methods are sufficiently 

 accurate for the solution of most problems, financial 

 calculations and certain geodetic operations constitut- 

 ing an exception, though even in these graphic 

 methods may play an important part. The first part 

 of the book deals with graphical algebra and graphic 

 methods of integration, the second with nomography. 

 The latter subject is treated from two points of view, 

 between which a kind of principle of duality exists — 

 the method of concurrent lines, and the method of 

 collinear points. In the former the relation between 

 three variables is determined by the intersection of the 

 lines corresponding to constant values of the respective 

 variables ; in the latter three straight or curved lines 

 are scaled, and the simultaneous values of the variables 

 are represented by collinear points on the scales which 

 can be read off by laying a ruler across them. In Prof. 

 d'Ocagne's hands this method has effected quite a re- 

 volution in simplifying numerical approximations, and 

 it has the merit of being easily extended to more than 

 three variables. 



MytbeiibiJduiig uiid Erhcnntnis. By G. F. Lipps. 



Pp. viii + 312. (Leipzig: B. G. Teubner, 1907.) 



Price 5 marks. 

 Tins is an interesting contribution to the literature 

 which in recent times has been filling up the gap be- 

 tween mathematics and philosophv. In it the author 

 traces the origin of mythical superstitions in primitive 

 races and their subsequent replacement by the critical 

 methods of exact analysis. He further discusses the 



NO. 2045, VOL. 79] 



application of symbolic methods to the representation 

 of phenomena connected with the universe, with ex- 

 istence, and with thought. The book forms a suitable 

 sequel to Poincare's " Science and Hypothesis," and 

 is published in the form of the third of a series of 

 books bearing the title of Poincare's volume. \A'hile 

 covering a somewhat dilferent field. Dr. Lipps's 

 method of treatment is more constructive in character. 

 He has attempted to build up a connected theory 

 rather than to ask the invariable question, Why? 



The Old Yellow Book. By Charles W. Hadell. 

 Pp. viii4-cclxii-t-345. (Washington : Carnegie In- 

 stitution, igo8.) 

 The first part of this large volume consists of a com- 

 plete photographic reproduction of the " Yellow 

 Book," now in the library of Balliol College, which 

 formed the theme of Browning's poem, " The Ring 

 and the Book." This is followed by an English trans- 

 lation, as well as translations of two other sources of 

 information relating to the Franceschini murder case, 

 and an essay by the author on " The Making of a 

 Great Poem." The photographic reproductions, as the 

 author points out, are of first importance to secure the 

 scholarly world against the possible destruction of the 

 unique copy in Balliol College. At the same time, 

 seeing that a few blemishes, due to creases in the 

 original book, have been remov'ed, and that the pages 

 have been re-numbered, it seems a pity that the present 

 book was not properly guillotined before being issued 

 to the public. 



LETTERS TO THE EDITOR. 



[The Editor does not hold himself responsible for opinions 

 expressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous communications.] 



On the Magnetic Aciion of Sun-ipots. 



It was perhaps to be expected that the recent discovery 

 of the Zeeman effect in the spectra of sun-spots should 

 revive the idea of a direct magnetic action originating 

 in the sun and observable at the surface of the earth. A 

 numerical estimate is therefore called for as to the magni- 

 tude of the disturbance which might be produced by such 

 a direct action. 



A solar vortex involving electric circulation, and con- 

 sequently magnetic fields, will be most favourably placed 

 to produce magnetic action if its apparent position is at 

 the centre of the solar disc. If we consider the dis- 

 turbed area, whicli for convenience I shall call the 

 spot, as a magnetic pole, the first question that arises 

 refers to the whereabouts of the opposite pole. We 

 may place it at the further end of the solar diameter 

 passing through the spot, and thus again assume the 

 most favourable conditions. If, now, the vertical forces 

 on the solar surface are treated as made up of a series 

 of spherical harmonics, we need only consider the first 

 term from which forces varying inversely as the cube of 

 the distance are derived, because the numerical values of 

 the forces derived from the higher terms are, at the 

 distance of the earth, at least a hundred times weaker. 

 Write, therefore, for the vertical force F 

 F = B/t + higher terms, 

 where /j. is the cosine of the solar co-latitude measured 

 from the spot. 



The coerticient B is determined in the usual wav bv 



Fl^dn = iB. 



As the spot is confined to a small region, for which 

 /i=i, and F has only finite values over this region and 

 at the opposite polo, we may for the . left-hand side of the 



