May 9, 1895] 



NATURE 



43 



Holtzmann appears to have performed an experiment similar to 

 Fresnel's with inclined mirrors; Trouton has drawn attention to 

 phenomena similar to those of thin plates ; and others have 

 experimented with wire gratings like those by means of which 

 Hertz demonstrated the polarisation of electric radiation : but 

 the great wavedength (about half a metre) of the oscillations 

 used has been a slumblingd)lock in the way of more delicate 

 experiments. Trof Righi has succee<Ied in producing oscilla- 

 tions having a wave-length as small as 2 '6 cm., and has devised 

 a novel form of resonator made by taking a strip of silvered 

 glass, dissolving away the varnish from the back, and drawing a 

 diamond-line across. He has thus been able to demonstrate the 

 analogy with other phenomena of optics, among which may be 

 mentioned : — PVesnel's interference-experiments with inclined 

 mirrors and biprism ; interference by reflection from thin plates 

 and by transmission through them ; diffraction by various means 

 (slits, edges, Kresnel's diaphragm) ; elliptic and circular polari- 

 sation ; and total reflection. The description of the experiments 

 is accompanied with full theoretical discussions ; and if Prof. 

 Righi does not aim at the general treatment which is suitable to 

 a treatise like I'oincare's, he, at any rate, succeeds admirably in 

 showing how^ the border-land between electricity and optics is 

 being actually explored. 



In another memoir,^ Prof. Righi develops Hertz's equations so 

 as to find the electromagnetic disturbance produced by the com- 

 bination of two small rectilinear electric oscillations at right 

 angles, say along the axes of z and _)', having equal amplitudes 

 but differing in phase by a quarter wavedength. Each of these 

 might be replaced by the mechanical movement of equal and 

 opposite electric charges, oscillating with pen<lular motion about 

 the origin along one of the axes. Two such mechanical motions 

 at right angles, differing in phase by a quarter wave-length, 

 would compound into a motion of uniform rotation in a circle 

 about the origin in the plane of zy. The disturbance due to 

 such a circular motion of equal and opposite charges would, with 

 certain limitations, be the same as the disturbance produced by 

 the combination of the two rectilinear oscillations first considered. 

 Prof, Righi shows that it takes the form of a spherical wave 

 haxHng its centre at the origin of coordinates. The vibrations 

 are in general (to use the language of optics) elliptically polarised; 

 in the neighbourhood of the axis of .x they are circularly polarised; 

 in the equatorial ]>iane zy they are plane-polarised. 



In a third memoir, by Prof. H. A. Lorentz," an attempt is 

 made to establish a theory of electrical and ojitical phenomena in 

 connection with moving bodies. This naturally involves a dis- 

 cussion of the relation between the ether and ponderable Ijodies 

 in motion, and of the theories proposed by Fresnel and Stokes 

 resj^ctively. After weighing the evidence on both sides, the 

 Leyden professor is of opinion that Fresnel's conception ofiers 

 fewer difficulties than its rival. The question is of importance 

 in electricity as well as in optics ; it is necessarily raised by a 

 rigid examination of any electrical phenomenon, such as the 

 motion of a charged body or of a conductor carrying a current. 

 Prof. Lorentz bases his explanation of electrical phenomena on 

 the hyiKJthesis that all bodies contain small electrically charged 

 particles, and that all electrical processes depend upon the posi- 

 tion and motion of these *' ions." This conception of ionic 

 charges is universally accepted for electrolytes, and also forms 

 the most probable explanation of the convective discharge of 

 electricity in gases. It is here extended to pontlerable dielectrics, 

 the *' polarisation" of which is ascribed to the existence of such 

 particles in positions of equilibrium fnmi which they can only be 

 displaced by external electrical forces. The periodically chang- 

 ing polarisations which, acconling to Maxwell's theory, consti- 

 tute light-vibrations, here become vibrations of the ions. 



pv. 



SCIENCE IN THE MAGAZINES. 



A MOST interesting account of Madame Kovalevsky's eventful 

 •**■ life is contributed to the Fortttightiy by Mr. K. W. 

 Carter. The sketch is based upon that gifted mathematician's 

 own published rec<)llecti()ns, and Madame Edgren-I.effler's bio- 

 graphy of her lamented friend. As there are some who are not 

 familiar with the career of the subject of Mr. Carter's article, a 



1 " Sullu onde electromagnetiche generate da duo piccole oscillazJoni 

 ' It-tiriehc ortogonali oppure per me/zo di una rolazione uniforme." (Bologna : 



- " Versiich einer Theorie der elektrischen iind optischcn Erscheinungeti in 

 Wwegten Kilrpern." (I,eyden : 1895). 



NO. 1332, VOL. 52] 



short summary of the chief points may be of interest. Sophie 

 Kovalevsky was bom at Moscow about 1S50, where the first five 

 years of her life were spent. Her father then removed to PaHbinu, 



i in the government of Vitebsk. It was there that her l>ent for 



[ mathematics first showed itself .\ room had been [)apered with 

 old disused ]5rinting paper, amongst which were several sheets 

 of Ostrogradski's lectures on the differential and integral 

 calculus. "This room possessed a strong fascination for the little 

 seven-year-old maiden. Here she was Co be found daily, her 

 attention riveted on these walls, striving to imderstand some- 

 thing of the strange figures and stranger formulas. 'I re- 

 member,' says Madame Kovalevsky, ' that every day I used to 

 spend hours before these mysterious walls, struggling to under- 

 stand some of the sentences, and to find the order of the sheets. 

 By dint of long contemplation, some of the formulas became 

 firmly fixed in my menior)-, and even the text, though I Cf»uld 

 comprehend nothing of it at the time, left its impres.sion on my 



j brain.' When several years later, her father was jjrevailed oh 

 to let her have some instruction in mathematics, the results were 

 a surprise and a revelation to all concerned : not least to the little 

 pupil herself The mysteries of the walls now grew clear, and 

 her progress was made '.by leaps and bnunds. The diiferential 

 calculus presented no difficulties to her, and her tutor found that 

 she knew the formulas by heart, and arrived at solutions antl 

 explanations quite independent of his aid." 



In October, 1S68, Sophie Kroukovsky contracted the romantic 



I marriage with \'ladimir Kovalevsky, and the two went to Heidel- 

 berg as students at the University. .After tW(;> terms spent at 

 Heidelberg, she moved to Berlin, where she worked for four years 

 under the direction of l*rof. \Veierstras.se. '* the father of modern 

 mathematical analysis." During this period, she wa.s occupied 

 in writing the three important treatises which subsequently 

 gained for her the degree of Doctor in Philosophy at Gottin- 

 gen. Passing over the next few years in Madame Kovalevsky's 

 life, during which her husband died, we come to the winter 

 of 1S83-84, when .she went to Stockhi'lm as the " Docent "' 

 of Prof. Mitlag-Lefller. K course of lectures delivered 



I during the winter session led to her appointment to the 

 chair of higher mathematics at the University of Stock- 



i holm, in July, 1884, a post which she occupied until her 

 death. The crowning scientific labour of her life was the 



I treatise which gained for her the Bordin prize of the Paris 



' .\cademy in 1888. The .subject proposed was "To perfect in 

 one important point the theory of the nitjvement of a .solid body 

 round an immovable point,"' and in rectujnition of the extra- 

 ordinary merits of Mdme Kovalevsky's work, the judges raised 

 the amount of the prize from three thousaml to five thousand 

 francs. But the distinguished authoress diil not live many years 

 to enjoy the high position she had gaine<l. In February, 1S91, 

 she was attacked by an illness which ended fatally after three or 

 four days. So passed away a woman of magnificent gifts, who, 

 "Taking the direction of her life into her own hands, an<l 

 choosing for herself one of the steepest p,aths to fame, .she 

 traver.sed it with swift and steady steps." 



Mr. W. H. Hudson contributes to the I'orlnightly an article 

 on " The Common Crow," a bird which he finds from inquiries, 

 " is no longer to be found as a breeder, <ir is exceedingly rare, 

 in districts where game is very strictly preserved ; but that in the 

 wilder counties where game is not strictly preserved, in woode<l 

 hilly places, he still exists in diminished numbers as a breeding 

 s|>ecies.'" .\nother article in the same magazine, on " Danish 

 Butter Making,", by Mrs. .\lec Tweedle, furnishes instructive 

 reading for British agriculturists. 



The remarkable growth of electric railroad mileage in the 

 United .States, during the past five years, is brought out in an 

 article by Mr. Jo.scph Wetzler, in Scrihiitr. " .\t the present 

 time," he says, " there are over eight hundred and fifty electric 

 railways in the United States, operating over 9000 miles of 

 track and 23,000 cars, and representing a capital investment of 

 o\et four hundred million dollars. What stu])endous figures, 

 when we consider that in 18S7 the number of such roads 

 amounted to only thirteen, with scarcely one hundred cars!" 

 ,\ quotation from a paper in the series on "The .\rl of 

 Living,' cimtributed by -Mr. Kobert Crant to the same 

 magazine, is worth giving here. '" There are signs (hat 

 these in charge of our large educatitmal institutions all 

 over the country are beginning to recognise that ri)>e 

 scholarship and rare abilities .as a teacher are entitled to 

 be well recompensed pecuniarily, and that the breed of such 

 men is likely to increase somewhat in proportion to the size and 

 number of the prizes offered. Our college presi<lents and 



