110 



DISCOVERY 



tific talks and demonstrations of a popular kind should 

 see it. 



The Mathematical Theory of Relativity. By A. S. Edding- 

 TON, M.A., F.R.S. (Cambridge University Press, 



205.) 



This is a systematic and comprehensive treatise on the 

 mathematical theory of relativity, written for physicists 

 possessing a strong mathematical equipment who have 

 already obtained a general acquaintance with the theory 

 in a less technical form such as from the author's previous 

 book, Space, Time and Gravitation. It formulates mathe- 

 matically the new conception of the world described 

 in the other work, and follows out the consequences to 

 the fullest extent. It should take its place as the standard 

 mathematical work in English on relativity. 



A. S. R. 



Books Received 



(Mention in this column does not preclude a review.) 

 MISCELLANEOUS 

 Primitive Ordeal and Modern Law. By H. Goitein. 



(George Allen & Unwin, Ltd., 105. 6rf.) 

 The Religion of Science. By Prof. Willi.\m H.\milton 



Wood. (Macmillan & Co., Ltd., 6s.) 

 Supplying Britain's Meat. By George E. Putnam, 



B.Litt. (George G. Harrap & Co., Ltd.) 

 Great and Small Things. By Sir Ray Lankester, 



K.C.B., F.R.S. (Methuen & Co., Ltd., 7s. 6d.) 



PHILOSOPHY AND PSYCHOLOGY 

 Psychological Types, or The Psychology of Individuation. 

 By C. G. Jung, M.D., etc. Translated, with an 

 Introduction, by F. G. Baynes, M.D. (Kegan Paul, 



25^-) 



Hypnotism and Suggestion. By Louis Satow. Translated 



by Bernard ^Iiall. (George Allen & Unwin, Ltd., 



1 05. Qd.) 

 Duality. A Study in the Psycho-analysis of Race. By 



R. N. Bradley. (George Routledge & Sons, Ltd., 



6s. 6^.) 

 The Soul of the State, or (The Know Thyself). By Phil. 



Al. Phil. Vol. I. (Printed by Athanasios Papas- 



P5n:ou, Athens.) 



SCIENCE 



Suggestions for the Prevention of the Decay of Building 

 Stone. By J. E. Marsh, M.A., F.R.S. (Basil 

 Blackwell, is. 6d.) 



The Constitution of the Universe. By Louis Stromeyer, 

 A.R.S.M. (Bangalore : Higginbothams, Ltd., Rs. 6.) 



Wind and Weather. By Alexander ;\IcAdie. (Mac- 

 millan & Co., 5s.) 



Crystallisation of Metals. By Col. N. T. Belaiew, 

 C.B. (University of London Press, js. 6d.) 



Our Solar System and the Stellar Universe. By Rev. 

 Charles Whvte, LL.D., F.R.A.S. (C. Griffin & 

 Co., Ltd., los. 6d.) 



Geology. " Science for All" Series. By C. I. Gardiner, 

 M.A., F.G.S. (John Murray, 3s. 6d.) 



The Elementary Principles of Lighting and Photometry. 

 By John' W. T. Walsh, M.A., M.Sc, F.Inst.P. 

 (Methuen & Co., Ltd., los. 6d.) 



The Structure of Atoms. By Dr. Alfred Stock. Trans- 

 lated by S. Sugden. (Methuen & Co., Ltd., 6s.) 



Richter's Organic Chemistry. Vol. Ill — Heterocyclic Com- 

 pounds. Translated by E. E. Fournier d'Albe, 

 D.Sc. (Kegan Paul, Trench, Triibner & Co., Ltd.. 

 25^.) 



Correspondence 



Sir, 



RAINFALL AND CIVILISATION 



To the Editor of Discovery 



With respect to Colonel Haig's very interesting 

 article on the above, might I suggest that the movement 

 of the earth's axis, known as " Precession," might be the 

 cause of the shift northwards of the desert belt which 

 he so clearly points out ? This movement of the earth's 

 axis must, of course, involve a correspondingly slight 

 shift in the tilt of the plane of the earth's equator to the 

 ecliptic. It thus necessarily follows that there must 

 be a slight shift, north and south of the earth's equator, 

 of the sun's maximum heat. The desert belts must 

 reciprocate this shift. There is, therefore, a true scientific 

 basis for his statements. Theoretically the desert belts 

 ought to shift north and south under the action of Pre- 

 cession. Colonel Haig has shown that they do so. 

 According to Professor Young, " At present the pole star is 

 about i;^ ° from the pole. At the time of the star catalogue 

 of Hipparchus it was 12° distant from it, and during the 

 next two centuries it will approach to within about 33', 

 after which it will recede." Therefore in two centuries 

 from now the northern limit in the shift of the desert 

 belts will be reached and the southern shift begin. Spain, 

 Persia, etc., may therefore expect their rainfall to decrease 

 very slightlv during the next two centuries. After this 

 their rainfall will increase, and it will be 25,867 years 

 (the period of Precession) before a similar state of things 

 returns. The Mediterranean basin, etc., have, therefore, 

 not much more to fear on account of increased scarcity 

 of rain. They will become fertile again as the desert 

 belt shifts southwards in response to the Precessional 

 movement. 



Another piece of e\idence of shift in this belt is that of 

 ancient Canaan. See [inter alia) Num. xiii. 23, 27, and 

 Deut. viii. 7, 8. The dates here involved fall in remarkably 

 well with the Precessional period. From three to four 

 thousand years ago the Near East and the Mediterranean 

 basin could and should have had much more rain than to- 

 day. In another four or five thousand years they will 

 again be fertile and remain so for about fifteen thousand 

 years ; after\vhich the drought will again be setting in. 



Yours, etc., 



H. J. Allen. 

 Treales Vicarage, 

 Kirkham, 

 Langs. 

 December 29, 1922. 



