246 



NATURE 



[July 16, 1903 



Das Gesetz der Translation des Wassers. Von T. 



Christen, Oberforster. Pp. viii + 179 ; with one 



lithographed plate. (Leipzig : Wilhelm Engelmann ; 



London : Williams and Norgate, 1903.) 

 Much has been written about the flow of water in 

 pipes, channels, and rivers, considered from the point 

 ■of view of the hydraulic engineer, and many attempts 

 have been made to obtain empirical formulae for pur- 

 poses of numerical calculation. In this volume the 

 -author proposes the formula z/ = -^</(QI)/ t'B, where v 

 is the mean velocity, Q the total flow per second, I 

 the gradient as a sine, and B the half-breadth of the 

 channel. A comparison of the results of the author's 

 formulae is made, both with the results of experi- 

 ment and with those of other writers, especially 

 Bazin, and calculations are given of the velocity curves 

 for difl'erent sections and under different conditions. 

 Reynolds's critical velocities are also discussed. The 

 book contains a bibliography, tables of coefficients, and 

 a diagram of the author's experiments and of velocity 

 curves. 



The new laws are admittedly only empirical, and the 

 author Indicates that many points might with advan- 

 tage be discussed at greater length, but he has cer- 

 tainly succeeded In Including a large amount of im- 

 portant and suggestive information In a book of 

 small compass, and his theories will.be read and dis- 

 cussed with the greatest interest by hydraulic engineers 

 and experimenters who have worked in the subject. 



Colloquies of Common People. By James Anstie, 

 K.C. Pp. 530. (London: Smith, Lider and Co., 

 1902.) 

 The English language contains few good specimens 

 ■of the philosophical dialogue, perhaps none except the 

 masterpieces of Berkeley. In attempting to revive 

 this most difficult form of composition Mr. Anstie has 

 ventured on a daring task, and I fear cannot be said 

 to have achieved a great success. Like others before 

 him, he forgets that a dialogue Is Intolerable unless 

 its author Is dramatist enough to confer Individual 

 character on the interlocutors ; nothing Is heavier read- 

 ing than wedges of disquisition by mere puppets. Of 

 the variety of topics handled by Mr. Anstie 's puppets It 

 Is impossible to give any summary, as they appear to 

 begin their discussion anywhere and to argue anyhow. 

 They seem, however, in the course of his five hundred 

 ■ odd pages to touch on most of the current topics of 

 ethics and psychology. The reader should at least 

 have been assisted to follow their excursions by a table 

 of contents and an Index. A. E. T. 



A Country Reader. II. By H. B. M. Buchanan, 

 B.A. (Cantab.). Pp. vIIi-+233; with illustrations. 

 (London: Macmlllan and Co., Ltd., 1903.) Price 

 IS. 6d. 

 As Mr. Buchanan says, a child is much more likely to 

 learn to read fluently and with intelligence If his read- 

 ing book Is concerned with subjects falling within his 

 everyday experience, and from this point of view the 

 set of readers, of which this is the second, will prove 

 useful and popular in rural primary schools. The 

 various sections of the book deal In simple, Interest- 

 ing language with the characters and uses of the goat, 

 th.^ donkey, the cat, our common reptiles, the fish of 

 our ponds and streams, pastures and grasses. The 

 illustrations are numerous and exceptionally good, 

 though it is a pity the author has omitted to Indicate 

 the scale of the drawings; there Is some fear, for in- 

 stance, that quite a wrong Idea of the relative sizes 

 of the carp and minnow will be obtained by the pupil 

 from the pictures which face one another on pp. 96 

 and 97. 



NO. 1759, VOL. 68] 



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.] 



Gases Occluded by Radium Bromide. 



Rutherford and Soddy {Phil. Mag., 1902, p. 582 ; 1903, 

 p. 453 and 579) pointed out that the almost invariable 

 presence of helium in minerals containing uranium indicated 

 that that gas might be one of the ultimate products of the 

 disintegration of the radio-elements. Rutherford, more- 

 over, determined the mass of the projected particle which 

 constitutes the " a-ray " of radium (Phil. Mag., 1903. 

 p. 177) to be approximately twice as great as that of the 

 hydrogen atom, an observation which points in the same 

 direction. These a-particles are readily absorbed by solids, 

 and should accumulate in the solid salts of radium and in 

 the radio-active minerals. 



We have been engaged for some months in examining 

 the spectrum of the " radio-active emanation " from 

 radium, and during this work the opportunity presented 

 itself of examining the gases occluded by 20 mgrs. of radium 

 bromide which had been kept for some time in the solid 

 state. These gases, which are continuously generated, 

 have already been partially examined by J:heir discoverer, 

 Giesel, and by Bodlander {Ber. deutsch. chem. Ges., 36. 

 p. 347), and found to consist mainly of hydrogen and some 

 oxygen. We have found that after removing hydrogen and 

 oxygen from the gases evolved from 20 mgrs. of radium 

 bromide, the spectrum showed the presence of carbon 

 dioxide. On freezing out the carbon dioxide, and with it. 

 a large proportion of the radium " emanation," the residue 

 gave unmistakably the D3 line of helium. This was con- 

 firmed by sealing off the tube, and comparing its spectrum 

 with that of a helium tube. The coincidence of the two 

 lines may be taken to be at least within i/ioth of the 

 distance between D^ and D^, or say 0-5 of an Angstrom unit. 



This observation, if confirmed, substantiates the theory 

 already mentioned, and brings ordinary methods to bear 

 on the changes occurring in radio-active bodies. 



William Ramsay. 



July 10. Frederick Soddy. 



P.S. (July 13). — We have repeated the experiment with 

 30 mgrs. of fresh radium bromide, kindly placed at our 

 disposal by Prof. Rutherford, which had probably been 

 kept for several months in the solid state. Entirely new 

 apparatus was constructed for the purpose, and better pre- 

 cautions were taken to exclude from the spectrum tube 

 carbon dioxide and the emanation. The spectrum was 

 practically that of pure helium, with the addition of two 

 new lines. The lines identified are : — 



4932 

 4713 

 4472 



The additional lines are one in the red and one in the 

 green ; these we have been unable to identify. 



The Extirpation of Culex at Ismailia. 



I BEG to enclose for publication the translation of a 

 report received from the general secretary of the Suez Canal 

 Company regarding the effects of the anti-malaria cam- 

 paign at Ismailia since the visit of Sir William MacGregor 

 and myself last September. While it is obviously too early 

 to speak definitely regarding the result on the rnalaria rate, 

 the secretary is able to announce that mosquitoes of the 

 genus Culex " ont 6t6 supprimes d'une manni^re presque 



