556 



NA TURE 



[September 27, 1906 



or 5 rays eniiUed by polonium, and which indicate that 

 negatively charged secondary rays are produced when an 

 aluminium or copper plate is bombarded by a stream of 

 « rays. 



The method used may be briefly described as follows : — 

 A polonium-coated copper disc was placed in a glass tube 

 •with its active side facing, and parallel to, a highly in- 

 sulated metal disc of the same size, which could be con- 

 nected to one pair of quadrants of a sensitive Dolezalek 

 ■electrometer. The distance between the discs could be 

 adjusted. The polonium disc could be raised to any 

 required potential by connecting it to a battery of small 

 secondary cells. The glass tube was evacuated by means 

 of a mercury pump down to a pressure of about oooi mm. 

 and then sealed off, and the vacuum was then rendered 

 as high as possible by the use of Dewar's method. The 

 apparatus was placed between the poles of an electro- 

 magnet in such a manner that a magnetic field could be 

 ■applied in a direction at right angles to the straight Ime 

 joining the centres of the discs. The charge acquired in a 

 given time by the insulated disc, when different strengths 

 ■of magnetic field were applied, and when the electric field 

 between the discs had different values, was measured. 

 Tables of results are given, and these are also plotted in 

 the form of curves, showing the variation of the_ current 

 between the discs with varying magnetic and electric fields. 

 From the results obtained the author arrives at f±ie follow- 

 ing conclusions : — 



(i) That under ordinary conditions, i.e. when not acted 

 upon by an electric or magnetic field, the polonium gives 

 off a larger amount of negative than of positive rays. 



(2) Under the influence of a gradually increasing electric 

 field more and more of the slowly-moving negative rays 

 are stopped, and the charge carried by the a rays becomes 

 more and more predominant. 



(3) A potential difference of about lo volts between the 

 plates is sufficient to stop the last of the 5 rays. 



(4) The slowly-moving negative rays can also be pre- 

 vented from striking the insulated plate by curling them 

 up in a magnetic field. When they are stopped in this 

 latter way, however, the quantity of positive electricity 

 received by the insulated plate is only about one-fifth of 

 that received when an electric field is used to stop the 

 5 rays. The author explains this last fact as follows :— 

 When the potential difference between the two plates is 

 10 volts or more (the polonium being positive), the positive 

 current from the polonium to the other plate consists of 

 two parts, viz. a stream of positive o particles in the direc- 

 tion of the current, and a stream of negative particles in 

 the opposite direction given off by the insulated plate. A 

 magnetic field curls up this latter stream of negative rays, 

 as well as the 5 rays given off by the polonium. 



The author also points out that his results showing the 

 magnetic and electric deflection of the 8 rays are not in 

 agreement with those obtained by Ewers with another 

 sample of polonium. 



Paris. 



Academy of Sciences, September 17.— M. Troost in the 

 chair— The International Congress for the Study of the 

 Polar Regions ; G. Bigourdan. The congress was held 

 at Brussels on September 7, and was attended by delegates 

 representing fifteen countries and eighty learned societies. 

 Seven standing committees were formed, each concerning 

 itself with a special group of sciences. The formation of 

 an International Polar Commission was decided upon, and 

 bye-laws drawn up.— The deviations from the vertical in 

 the region of the Sahel, Algeria : R. Bourgeois. In the 

 triangulation of Algeria, the summit of the Voirol column 

 was taken as the junction of the network of triangles. 

 The national observatory, founded some years later, is 

 about 5 kilometres in a direct line from this column. If 

 the astronomical latitude of the observatory is compared 

 with the geodesic latitude of the same point, the calcula- 

 tion being made starting with the fundamental coordinates 

 of Voirol a relatively considerable discrepancy is found, 

 indicating' a strong deviation from the vertical at one or 

 other of these two points. In the present paper it is 

 shown that it is the Voirol station which is at fault, and 

 hence all the data built on this as a starting point require 



NO. 1926, VOL. 74] 



re-calculation. — The action of fluorine on chlorine, and on 

 a new method of formation of hypochlorous acid : Paul 

 Lebeau. Attempts were made to combine fluorine with 

 chlorine, under varying conditions, at temperatures ranging 

 from 0° C. to —80° C. It was found that fluorine and 

 chlorine do not combine directly. Liquid chlorine dis- 

 solves fluorine, but this fluorine is given off at the solidify- 

 ing point of the chlorine. In presence of water, fluorine 

 oxidises chlorine, the latter being completely converted into 

 hypochlorous acid, thus giving a new method for the pre- 

 paration of this acid. — Syntheses in the quinoline group : 

 phenylnaphthoquinoline dicarboxylic acid and its deri- 

 vatives: L. J. Simon and Ch. Mauguin. — The action of 

 mixed organomagncsium compounds upon amides : Con- 

 stantin Beis. To secure a reaction in all cases it is neces- 

 sary to prepare the organomagncsium compound in the 

 presence of the imide, the alkyl halide being added to a 

 mixture of the imide, magnesium, and ether. Iso- 

 indolinones, isomeric with arylamidoketones, are obtained. 

 — The haemopoietic activity of the different organs in the 

 course of the regeneration of the blood : Paul Carnot and 

 Mile. CI. Deflandre. — The experimental infection of 

 trypanosomiasis by naturally infected Glossina palpalis : 

 L. Cazalbou. Two out of seven specimens of Glossina 

 palpalis, captured on the banks of the river Bani, a large 

 tributary of the Niger, have infected dogs with trypano- 

 somiasis. A cat was similarly infected. — The movement of 

 the pole at the surface of the earth : Marcel Brillouin. 

 A discussion of the curves published by M. Albrecht since 



CONTENTS. PAGE 



Some Recent Works on Philosophy 533 



Sea-Fisheries Administration and Research . 535 



An Encyclopaedia of Physics 536 



Garden-Botany 537 



Our Book Shelf : — 



Meldrum : " Avogadro andiDalton. The Standing 



in Chemistry of their Hypotheses." — A. S. 537 

 Gruner : "Die radioaktiven Substanzen und die 



Theorie des Atomzerfalles." — F. S 538 



Moulton : " Introduction to Astronomy." — W. E. R. 53S 

 Letters to the Editor : — 



The Recent Radium Controversy. — Lord Kelvin, 



O.M., F.R.S 539 



Stress in Magnetised Iron.— Dr. C. Chree, F.R.S. . 539 



The Rusting'of Iron.— J. Newton Friend ... 540 

 The Mixed Transformation of Lagrange's Equations. 



—A. B. Basset, F.R.S 54° 



Suspended Germination of Seeds. — H. B. P. ... 540 



Optical Illusions on Electric Fan.— T. Terada . . 54" 



Aquatic-dwelling Weevils. — E. E. Lowe 541 



Remarkable Rainbow Phenomena. — George C. 



Simpson ; Rev. C. S. Taylor 541 



Some Scientific Centres.- IX. The Metallurgical 

 Department of the Sheffield University, {///iis- 



tratcd.) 54> 



Earth-Eaters in India. By N. W. T 543 



Notes 544 



Our Astronomical Column : — 



Astronomical Occurrences in October 548 



The Total Solar Eclipse of January, 1907 54S 



Observations of Phiebe in May and June, 1906 . . . 548 



The Colours of Sun-spots 54^ 



Colours and Magnitudes of Double Stars ..... 549 



Rotation Period of Jupiter's Equatorial Region . . . 549 



Geology at the British Association. By J. L. . . 549 

 Zoology at the British Association. By Dr. J. H. 



Ashworth 55° 



The Royal Photographic Society's Annual Exhibi- 

 tion. By C. J 553 



Geodetic Operations in South Africa. By W. E. P. 554 



University and Educational Intelligence 554 



Societies and Academies 555 



