July 9, 1908J 



NA TURE 



A few years ago I sifted all my observations at tlie 

 Julv and August periods with a view to find the most 

 active radiants determined at Bristol, and the number of 

 meteors recorded from them. Omitting Pcrseids, the 

 following is a list of the principal systems : — 



Periods 



The complete table of showers, rich and feeble, appeared 

 in Asltonomische Nachricbtcn, No. 3874. .\bout eighty- 

 five systems in all were displayed between July ib and 

 August 20. 



It would be interesting if some of these streams could 

 be re-observed during the oncoming return of the Perseids 

 and their radiant points re-determined. The positions 

 given in the table may be relied on as accurate to within 

 2° of probable error, but some of the radiants are more 

 exact than others, the centres having been more sharply 

 defined. In the case of showers of swift, strealiing 

 meteors, the intersecting points of the flights can generally 

 be ascertained with great precision. 



Special attention seems necessary to be given to the 

 period about July 11-12, when the first signs of the 

 Perseids decidedly begin to be manifested. 



This year moonlight will seriously interfere with 

 observations for about a week near July 13 and -August 12. 

 The maximum display of Perseids will be partially over- 

 powered by the radiance of our satellite, but some brilliant 

 meteors will be observed at about the epoch .'\ugust 9-13 

 should the skies be clear. W. F. Denning. 



MAGNETIC RESOLUTION OF SPECTRAL 

 LINES. 



"DROF. P. ZEEM.AN, continuing his investigations on the 

 occurrence of asymmetric separation of spectral lines 

 in a magnetic field (see Nature, April 30, vol. Ixxvii., p. 

 615), describes a series of observations on asymmetrical 

 triplets (Konink. Akad. Wetens. Amsterdam, p. 566, 

 March 27). As a method giving independent confirmation of 

 the previous work was desirable, he decided to investigate 

 the new series by means of the Fabry and Perot interfero- 

 meter, using the italoii — that special form of the instru- 

 ment In which the distance between the silvered surfaces 

 is kept constant, about 5 mm. The variations of wave- 

 length may in this case be determined either by continued 

 measurements of the saine interference ring or by the 

 method of coincidences, regulating the magnetic force in 

 such a manner that a ring which expands bv increasing 

 magnetic intensity coincides with a contracting ring. The 

 system of rings was formed in the focal plane of a small 

 achromatic lens of iS mm. aperture and 12 cm. focus. 

 This focal plane coincided exactly with the plane of the 

 slit of .a one-prism spectroscope, the width of the slit being 

 so reduced that the rings produced by the two yellow 



NO. 2019, VOL. 78] 



mercury lines at AA. 5791 and 5770 could be observed 

 separately. 



Reproductions of the appearances presented with 

 magnetic field off and on are included with the paper, 

 made from enlarged negatives. The measurements given 

 indicate conclusively that the positive results concerning 

 asynmietric resolution in strong fields have a real signifi- 

 cance, and a very interesting discussion of the results 

 is appended. Taking Lorentz's equation for determining 

 c/m, and accepting J. J. Thomson's value of e = i-iXio-^° 

 (electromagnetic units, the number of electrons per unit 

 volume causing the radiation of the yellow mercury line 

 5791 in a vacuum tube appears to vary from 8x10" to 

 4X10'° with magnetic fields varying from 29,220 to 9130 

 (laussian units. In these experiments the temperature of 

 ihe vacuum tube was between 100° C. and 120° C. ; the 

 corresponding vapour pressures of mercury, according to 

 Hertz, would be 0.29 mm. and 0.78 mm. respectively, and 

 it is calculated that the number of electrons participating 

 in the emission of line \ 5701 is of the same order of 

 magnitude as the number of atoms present. 



A number of observations made by Mr. Jack in the 

 physical laboratory at Gottingen are also recorded, show- 

 ing the asymmetrical separations of lines of wolframium 

 and molybdenum. The paper concludes with a question 

 as to the possibility of the wave-length of the central 

 line of a triolet beiritf changed bv the action of the mag- 

 netic field as compared with the unmodified line, and some 

 observations made with an echelon appear to indicate that 

 some lines undergo in strong fields displacements of the 

 order of six or ten thousandths of an Angstrom unit, in 

 most cases towards the red. This is to be further treated 

 in a subsequent paper. 



SOCIAL A\THROPOLOGY. 



pROF. J. G. FRAZER has made a good start in the 

 work of his chair at the University of Liverpool by 

 his opening address on " The Scope of Social Anthro- 

 pology." It is characterised by all the lucidity of exposi- 

 tion and grace of style which we are accustomed to expect 

 from the author of "The Golden Bough." His main 

 object is to plead for the systematic study of savages, who 

 represent an arrested, or rather retarded, stage of social 

 development. They are, he is careful to point out, primi- 

 tive only in a relative, not in an absolute, sense : that is, 

 they are primitive in comparison with ourselves, not in 

 comparison with primaeval man, of whom we know 

 nothing, and, so far as we can see at present, are likely 

 to learn nothing. 



The province of social anthropology falls into two depart- 

 ments, one embracing the customs and beliefs of savages, 

 the other including such relics of these as have survived 

 in the thought and institutions of more cultured peoples. 

 The first department mav be called the study of savagery, 

 the second the study of folk-lore. The government of 

 mankind, he goes on to show, is always and everywhere 

 essentially aristocratic, that is to say, the ^ dull-witted 

 majority always follows the keener-witted minority. In 

 the mental, no less than in the physical sphere, the 

 struggle is internecine ; but in the end the better ideas, 

 which we call the truth, carry the day. Hence, even in a 

 civilisation like our own, we find the lower classes still 

 following magical and other primitive practices of the same 

 kind. Not that schemes for the regeneration of society 

 form part of his programme. The study of the past must 

 throw light upon the problems of the present, but the 

 exploration of schemes of social reform is the business of 

 the sociologist, not of the social anthropologist. 



Dr. Frazer closes a remarkable address by an 

 impassioned appeal for the more careful study of that 

 savagerv which is so rapidly disappearin •;. "How shall 

 we of this generation look when we stand at the bar 

 arraigned on a charge of high treason to our race, we 

 who neglected to study our perishing fellow-men, but who 

 sent out costlv expeditions to observe the stars and to 

 explore the barren ice-bound regions of the poles, as_ if 

 the polar ice would melt and the stars would cease to shine 

 when we are gone? " 



