March 24, 1898] 



NA TURE 



48. 



a pygmy, who had been brought from Central Africa 

 by an Egyptian official called Baurtet, at his court to 

 dance and to amuse him. About seventy years later 

 another king, Pepi II., sent a despatch to Heru-khuf, 

 his officer commanding the garrison at Aswan or Syene, 

 in which he promised him a greater reward than was 

 conferred by Assa upon Baurtet if he would go and bring 

 back for him a pygmy "alive and in good health." In 

 the inscription which covers the walls of Heru-khufs 

 tomb at Aswan (see Schiaparelli, " Una Tomba Egiziana," 

 Rome, 1893), an account is given of the countries 

 through which this brave officer passed, and though it 

 is impossible to identify accurately all the places named, 

 it is perfectly clear that, like the officer Una, he passed 

 through the lands of great trees south of Khartum, and so 

 on to the districts described by Stanley (" Darkest 

 Africa," i. p. 198; ii. p. 40) and Schweinfurth (" Im 

 Herzen von Africa," ii. p. 131 ff.), to the land of the 

 pygmies. The pygmies were so well known in Egypt 

 that a reference to them is made in a version of the 

 "Book of the Dead" of the sixth dynasty. In the 

 temple at Karnak is an inscription of a later period 

 which states that " the pygmies came from the lands of 

 the south to do service in it," and in it, as in the earlier 

 texts, no doubt can be entertained as to the correctness 

 of the identification of the word ienk with "pygmy," for 

 in each case it is followed by the determinative of a 

 thick-set, stunted little man. We are hardly justified in 

 assuming that the Egyptians had any dominion de facto 

 in Central Africa, but there is no doubt that as far back 

 as the time of the fifth dynasty they were well acquainted 

 with the products and people of that remote land. 



Again, on p. 21 the firmament of bronze which Mr. 

 Tozer describes is nothing but the square metal plate 

 which the Egyptians thought formed the sky and the 

 floor of heaven, which was supported by four mountains 

 or props placed one at each of the cardinal points ; from 

 this at night the stars were hung out like lamps, and in 

 fact one of the names for stars, khabestc, means nothing 

 but " lamp." The god Atlas is, of course, nothing but a 

 Greek form of the god Shu, whose functions were to 

 lift the sky up from the earth at dawn, to support it 

 during the day, and to let it down again at night. The 

 inscriptions of Egypt would similarly afford many an 

 explanation of passages in Mr. Tozer's book. 



Among minor matters it seems to us very doubtful if 

 the name Samos is derived from the Semitic shamah 

 (p. 5) ; the Arabic word kasdir is, of course, derived 

 from the Greek as Dozy showed (Suppl. ii. p. 355, 

 col. 2) ; it is very doubtful if the names " Asia " and 

 " Europe " are derived from the Assyrian words " to go 

 forth " (of the sun), and " to set " (of the sun) ; the 

 Peutinger Table was published in its entirety, and it is 

 only Desjardin's description of it which is unfinished 

 (p. 310) ; and we should have preferred the conical to 

 the elliptical projection of Ptolemy's map given on the 

 plate which faces p. 341. It only remains to say that so 

 far as it goes Mr. Tozer's book is good, and that the 

 classical portions of it have been carefully done ; in a 

 new edition we hope that the sources of the information 

 which we obtain from Greek and Latin writers, and which 

 may be traced to hieroglyphic and cuneiform records, 

 will be duly described and set forth. 



NO. 1482, VOL. 57] 



OUR BOOK SHELF. 



La Teoria del Raggi Rontgen. By Prof. Filippo Re. 



With two plates. Demy 8vo. Pp. 64. (Palermo : 



Alberto Reber, 1898.) 

 In the first three chapters the author discusses the exist- 

 ing theories which regard Rontgen rays as longitudinal 

 waves, molecular streams, and transverse waves of ex- 

 tremely short wave-length. He then proceeds to sum- 

 marise the various hypotheses which have been advanced 

 to account for the electro-dispersion of these rays, and 

 their capability of bending round obstacles. Chapter vi. 

 deals britfly with other kinds of new rays — namely, 

 Becquerel rays, Le Bon's rays, and Winkelmann and 

 Straubel's "spathofluoric" rays. A comparison of the 

 properties of X-rays with those of Hertzian electric oscil- 

 lations of considerable length, leads Prof Re to propound 

 the hypothesis that the former are electric waves of prac- 

 tically infinite length. This hypothesis, the author re- 

 marks, has close analogy with that proposed by Sir G. G 

 Stokes at Liverpool, who suggested that Rontgen rays 

 might be due to non periodic disturbances of the ether. 



In attempting to show how this theory accounts for 

 the physical properties of Rontgen rays. Prof Re has, of 

 necessity, left unanswered many questions which natur- 

 ally suggest themselves, and in answering others has 

 hardly made out a strong case in favour of his views. 

 He attributes absence of reflection to the great pene- 

 trating power and difl'usion of the rays, and absence of 

 observed polarisation to the impossibility of arriving at 

 any practical result with the means commonly employed ; 

 but these explanations can hardly be said to support the 

 present theory more than any other. To account for 

 cryptochroism the author has to suppose that, although 

 the waves are of practically infinite length, their lengths 

 are nevertheless of different magnitudes. We should 

 have liked to see the question of the magnetic deform- 

 ation of Rontgen and Lenard rays discussed in connec- 

 tion with the present theory. Why such rays should be 

 produced by an apparatus so different from a Hertzian 

 oscillator as a Crookes' tube, might also well be asked. 



The author's familiarity with current research affords 

 sufficient guarantee of his competency to put forward a 

 theory possessing certain points of novelty. We are still 

 so much in the dark as to the nature of Rontgen rays, 

 that every new theory is worthy of the careful consider- 

 ation of physicists. Without wishing to commit our- 

 selves, the theory of electric waves of very great length 

 strikes us at first sight as being no less plausible 

 than many of the other hypotheses which have been 

 propounded. 



A Text-book on Applied Mechanics. By Andrew 

 Jamieson, M.I.C.E., Professor of Electrical Engineer- 

 ing in the Glasgow and West of Scotland Technical 

 College. Vol. ii. Pp. xiii 4- 388. (London : Charles 

 Griffin and Co., Ltd., I897.) 

 This text-book, of which this is the second volume, was 

 written mainly for second and third year students of 

 applied mechanics. Parts i. and ii., which form vol. i., 

 deal with the principle of work and its applications, and 

 gearing ; the present volume, divided into Parts iii. tovi., 

 includes motion and energy, graphic statics, strength of 

 materials, and hydraulics. 



The volume is divided into fifteen chapters, called 

 lectures, though the ground covered in any one of them 

 is generally much greater than any teacher would attempt 

 in one lecture and numerous illustrative examples are 

 given at the end of ea< n chapter. It is refreshing to find 

 the author introducing the calculus so freely into a te.xt- 

 book primarily intended for science and art students. 

 In Part iii. the author discusses very fully such important 

 practical questions as the energy of fly-wheels, engine 

 governors, and the balancing of moving parts : the whole 

 section is a very complete and good one. The . next 



