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The life of James Clerk Maxwell
392
Book Notices.
[Jour. F r a n k . Inst.,
THE LIFE OF JAMES CLERK MAXWELL. W i t h Selections from his Correspondence a n d Occasional Writings. By Lewis Campbell, M. A., L L . D . , a n d W m . Garnett, M . A . L o n d o n : Macmillan & Co. This is a most c h a r m i n g book fiom its first to its last chapter. It is seldom that a great m a n is so fortunate in his biographers. In this case both gentlem e n were his friends a n d associates in his scientific work. A n y t h i n g which relates to the life of one who has done so m u c h to enrich a n d continue the work of Newton a n d F a r a d a y must h a v e great interest to scientific students. E v e n the history of his youthful days, m a d e up largely from a diary kept by his father, to w h o m he seems to h a v e b e e n m u c h indebted for the developm e n t of his great m e n t a l powers, is full of interest. T h e greater portion of the b o o k consists of correspondence between Prof. Maxwell a n d well-known scientific men, introduced in chronological order, with explanatory paragraphs by Mr. Campbell. Much valuable information in connection with his scientific researches is also contained in letters of a social character. Not the least attractive feature of the book is the insight which it gives us into the character of the man, whose every-day life was m a r k e d with an affectionate t e n d e r n e s s , large-heartedness a n d solicitude for the welfare of others, which is quite r e m a r k a b l e a n d which accounts for the love which all his associates bore to h i m a n d intensifies the regret that such a m a n should h a v e been t a k e n away before his time. E.A.S. VAHIATIONS OF THE SUN'S DIANETER.--M. Hilfiker, of the Neufch~tel Observatory, states that the variability of the sun's diameter is very perceptible, the greatest diameters coinciding with the m i n i m u m period of sun spots, the least with the m a x i m u m . Similar conclusions h a d b e e n previously indicated by F a t h e r Rosa, the colleague of F a t h e r Secchi.--Les Mondes, October 9, I884. DENSITY AND F I G U R E OF TIlE E A R T m - - T h e experiments of Cornu and Baille indicate a p r o b a b l e terrestrial density between 5"4 a n d 5"6, a n d they t h i n k t h a t the result of Baily, 5"67, is too large. Cavendish, in .I798, estim a t e d the m e a n density at 5"48. Reicle, in I837, at 5"44. All of these results confirm, in a r e m a r k a b l e m a n n e r , the anticipations of Newton, who, in Book III. of the " Principia, T h e o r e m Io." declared that the m e a n density of the earth must b e between five a n d six times that of water, Gen. D. F. Menabrea h a s revised the experiments of C a v e n d i s h with the torsion balance, a n d found certain disturbances which were overlooked. M a k i n g proper allowances for those disturbances, h e finds a m e a n value of 5"58. In a further investigation, h e applied Ivory's theorem to the special case of an ellipsoid of revolution, supposed primitively fluid, but composed of concentric layers of different densities, deducing a flattening of e ~ . ~ . T h e most recent geodetic labors h a v e shown that the terrestrial meridians are not all alike, a n d that consequently the earth is not a perfect ellipsoid. Moreover, there are singular anomalies at divers stations in the oscillations of the pendulum, which seem to show that the terrestrial mass is not distributed in uniform layers. T h e s e facts indicate the n e e d of new investigations suitable for completing those of Cornu a n d Baille.--Comfltes Rendus, F e b r u a r y 16, 1885.
Book Notices.
[Jour. F r a n k . Inst.,
THE LIFE OF JAMES CLERK MAXWELL. W i t h Selections from his Correspondence a n d Occasional Writings. By Lewis Campbell, M. A., L L . D . , a n d W m . Garnett, M . A . L o n d o n : Macmillan & Co. This is a most c h a r m i n g book fiom its first to its last chapter. It is seldom that a great m a n is so fortunate in his biographers. In this case both gentlem e n were his friends a n d associates in his scientific work. A n y t h i n g which relates to the life of one who has done so m u c h to enrich a n d continue the work of Newton a n d F a r a d a y must h a v e great interest to scientific students. E v e n the history of his youthful days, m a d e up largely from a diary kept by his father, to w h o m he seems to h a v e b e e n m u c h indebted for the developm e n t of his great m e n t a l powers, is full of interest. T h e greater portion of the b o o k consists of correspondence between Prof. Maxwell a n d well-known scientific men, introduced in chronological order, with explanatory paragraphs by Mr. Campbell. Much valuable information in connection with his scientific researches is also contained in letters of a social character. Not the least attractive feature of the book is the insight which it gives us into the character of the man, whose every-day life was m a r k e d with an affectionate t e n d e r n e s s , large-heartedness a n d solicitude for the welfare of others, which is quite r e m a r k a b l e a n d which accounts for the love which all his associates bore to h i m a n d intensifies the regret that such a m a n should h a v e been t a k e n away before his time. E.A.S. VAHIATIONS OF THE SUN'S DIANETER.--M. Hilfiker, of the Neufch~tel Observatory, states that the variability of the sun's diameter is very perceptible, the greatest diameters coinciding with the m i n i m u m period of sun spots, the least with the m a x i m u m . Similar conclusions h a d b e e n previously indicated by F a t h e r Rosa, the colleague of F a t h e r Secchi.--Les Mondes, October 9, I884. DENSITY AND F I G U R E OF TIlE E A R T m - - T h e experiments of Cornu and Baille indicate a p r o b a b l e terrestrial density between 5"4 a n d 5"6, a n d they t h i n k t h a t the result of Baily, 5"67, is too large. Cavendish, in .I798, estim a t e d the m e a n density at 5"48. Reicle, in I837, at 5"44. All of these results confirm, in a r e m a r k a b l e m a n n e r , the anticipations of Newton, who, in Book III. of the " Principia, T h e o r e m Io." declared that the m e a n density of the earth must b e between five a n d six times that of water, Gen. D. F. Menabrea h a s revised the experiments of C a v e n d i s h with the torsion balance, a n d found certain disturbances which were overlooked. M a k i n g proper allowances for those disturbances, h e finds a m e a n value of 5"58. In a further investigation, h e applied Ivory's theorem to the special case of an ellipsoid of revolution, supposed primitively fluid, but composed of concentric layers of different densities, deducing a flattening of e ~ . ~ . T h e most recent geodetic labors h a v e shown that the terrestrial meridians are not all alike, a n d that consequently the earth is not a perfect ellipsoid. Moreover, there are singular anomalies at divers stations in the oscillations of the pendulum, which seem to show that the terrestrial mass is not distributed in uniform layers. T h e s e facts indicate the n e e d of new investigations suitable for completing those of Cornu a n d Baille.--Comfltes Rendus, F e b r u a r y 16, 1885.