DISCOVERY 



53 



is specifically called upon to carry out its provisions. 

 The practice of employing a corpse as a sort of medium 

 into which to summon a spirit is common in the 

 magical papyri ; and earlier, in the first century 

 after Christ, the poet Lucan describes how a witch 

 conjured the spirit back into the body of one recently 

 slain. 



This probably belongs to the barbarities of exotic 

 magic which became more repulsive and more elaborate 

 as classical civilisation became overripe. The horror 

 of human sacrifice has always made it an appropriate 

 feature of Black Magic. Its practice for divinatorv 

 purposes is laid to the charge of Vatinius by Cicero. 

 Some instances of such divinatory human sacrifices 

 appear to be based upon a belief, which is very common 

 in many lands, that at the actual moment of death 

 the spirit is simultaneously in connection with both 

 worlds. Its connection with the ne.xt world gives it 

 supernatural intelligence ; its connection with this 

 world enables it to communicate it. The Arabs of 

 the Middle Ages, who employed criminals for this 

 purpose, often deliberatelv protracted the sufferings 

 of the victims in order to prolong the opportunities of 

 this intermediate state.' This theory too was known 

 in later classical antiquity, and calumny asserted that 

 Antinous, the beautiful favourite of the Emperor 

 Hadrian, was a voluntary victim to a magical sacrifice 

 of this character. 



Generally speaking, as our brief survey will have 

 suggested, although from a comparatively early date 

 in classical antiquity the belief in personal sur\aval 

 was common, and the possibility of communication 

 with spirits of the dead was not denied, its practice 

 was attempted not from scientific motives, nor in 

 order to regain touch with the beloved, but in order 

 to obtain knowledge of the future ; with the exception 

 of the ritual of hero-worship, which is not really 

 analogous to modern spiritualism, it was not highly re- 

 garded and belonged rather to magic than to religion. 

 (Concluded) 



BIBLIOGRAPHICAL NOTE 



The most important books dealing with these matters are 

 Rohde, Psyche : Seelenkult und Unsterblichkeiisglaube der 

 Griechen : and Farnell. Greek Hero Cults and Ideas of Immortality . 

 Some references with regard to necromancy are collected in 

 Halliday, Greek Divination. An entertaining, if slight, little 

 book is Collison Morley, Greek and Roman Ghost Stories 

 (Blackwell, 1912). Readers with a knowledge of Greek may 

 be referred to Headlam, " Ghost-raising, Magic and the 

 Underworld," Classical Review, xvi. The best short history 

 of Greek religion is Farnell, Outlitie-History of Greek Religion ; 

 the Orphic tablets which were found in Southern Italy are 

 discussed in Miss Harrison's Prolegomena to the Study of Creek 

 Religion. The influence of Orphism upon Greek thinkers 

 may be studied in Adam, The Religions Teachers of Greece. 



' See the passage in Ibn Khaldun referred to by Douttt-, 

 Magie et Religion dans I'Afrique du Nord, p. 401. 



Reviews of Books 



MATHEMATICS AND THE ATOM 



(a) Dimensional Analysis. By P. W. Bridgman. 



(London : H. Milford ; Xew Havtn : Vale Uni- 

 versity Press, 25s.) 



(b) The Theory of Spectra and Atomic Constitution. By 



Niels Bohr. (Cambridge University Press, js. bd.) 



(c) A Treatise on the Theory of Bessel Functions. By 



G. N. Watsox, Sc.D., F.R.S. (Cambridge Uni- 

 versity Press, 705.) 



(d) The Quantum Theory. By Fritz Reiche. Trans- 



lated by H. S. Hatfield and H. L. Brose. (Methuen 

 &Co.. 6s.) 



(a) The use of the methods of dimensional analysis 

 both in technical physics and in theoretical investigations 

 is growing, and, indeed, it is desirable at the present time 

 that every physicist should have this method of analysis 

 at his command. But, perhaps because the subject 

 appears so simple that a formal presentation of it is 

 unnecessary, no systematic exposition cif the principles 

 of the methods has preceded this one by the professor 

 of theoretical physics at Harvard. A subject, however, 

 must have a book about it sooner or later, and it is excel- 

 lent that the first one should be written by an acknow- 

 ledged expert on it. The book is, of course, chiefly for 

 those who have already some acquaintance with the 

 general method. It contains a systematic exposition 

 of the principles of the subject, and full illustration of 

 applications chosen to emphasise the points most commonly 

 misunderstood, like the nature of a dimensional formula, 

 the proper number of fundamental units, and the nature 

 of dimensional constants. References to previous work 

 are given in each chapter, and at the end of the book are 

 many problems for a reader to solve. But why is the 

 price of a book of a hundred and ten pages so high ? 

 The book should find acceptance by a wider circle of 

 readers than the price fixed for it indicates, for the sub- 

 ject, besides being interesting, is one easily followed by 

 many w-ho are neither widely read physicists nor pro- 

 found mathematicians. It is the first book on the subject, 

 on wlrich its author is a well-known authority, and, let it 

 be said, his exposition is very clear. The bock is based on 

 a series of lectures to a Graduate Conference at Harvard 

 two years ago. 



(6) All students of chemistry and physics will be 

 grateful to Prof. Bohr, of Copenhagen, for putting his 

 highly original and exceedingly profound theoretical work 

 on atomic structure in a form which they have at least 

 a chance of understanding. The book is a translation 

 of three essays written at different times in the past nine 

 years. In the third the author describes the remarkably 

 detailed view of the structure of the atom to which he has 

 been led, a view which attempts to explain the relations 

 summed up in the Periodic Table and to give a natural 

 reason for the occurrence of the rare earths. 



