May 4, 1883.] 



SCIENCE. 



365 



termination of the magnitude of certain electric 

 quantities, and tlieir relations to eacli other." 

 The Cavendish physical laboratorj- was not 

 opened until 1874. Maxwell died in 1879, five 

 years later. In this short term of office he left 

 the impress of his genius upon the scientific 

 work of Cambridge. Sir William Thomson has 

 said, " There is, indeed, nothing short of a 

 revival of physical science at Cambridge with- 

 in the last fifteen years, and this is largelj' due 

 to Maxwell's influence." We have said tliat 

 no one can thoroughly appreciate the genius 

 of the man who has not read his treatises on 



electricity, on heat, and his various essays, 

 which are soon to be collected and published. 



His life, with its great expressions of rever- 

 ence for higher things and its respect for true 

 scientific work, is one to ponder over ; and his 

 correspondence is rich in literary suggestions, 

 and enlivened by the play of liumor. It will 

 always be a source of gratification to Ameri- 

 cans to know that the American academj- of 

 arts and sciences and the American philo- 

 sophical society' were the first of the foreign 

 scientific societies to elect Maxwell a foreign 

 honorary member. 



WEEKLY SUMMARY OF THE PROGRESS OF SCIENCE. 



MATHEMATICS. 



The polar quadrilateral. — Given a conic and a 

 polar quadrangle : the five quadrilaterals got by taking 

 the poles of its vertices, or the pole of one vertex and 

 the lines joining the other three, are jjolar quadrilat- 

 erals such that conies circumscribing their diagonal 

 triangles osculate the given conic in the same six 

 points. S. Kantor gives a geometrical proof of this 

 theorem by showing that the six points in which a 

 conic inscribed in a quadrilateral can be made to 

 touch the given conic are the same for the five quad- 

 rilaterals, and that any one of the triply infinite num- 

 ber of conies with respect to which a fixed quadrilat- 

 eral is polar osculates other conies of the system in 

 the same six points in which it is touched by conies 

 inscribed in the quadrilateral. He points out an 

 application of the latter property to the determina- 

 tion of the points of inflection of the unicursal quartic 

 obtained by a quadric transformation of the conic. — 

 (Math. o?Hi., xxi. 299.) c. L. F. [754 



Theory of functions. — The second part of a 

 paper by Rausenberger treats of single valued func- 

 tions with non-interchangeable periods. It is not 

 convenient here to do more than refer to this pa- 

 per, as a review of it can hardly be given without 

 introducing a good deal of algebraical work. The 

 paper, however, as introducing a certain number of 

 new and interesting ideas, is decidedly worthy of con- 

 sideration. — (ilath. annal.jTLTii.) t. c. [755 



Impact of billiard-balls. — M. Eesal has gener- 

 alized some of the results obtained by Coriolis in his 

 TJieorie anah/tique des effets dujeu de hillard. Corio- 

 lis has considered the two balls as being homogeneous, 

 and possessing identical properties in every respect. 

 M. Eesal takes account of possible differences in the 

 masses of the two balls, and in their moments of 

 inertia with respect to a diameter, — two properties 

 which mi^ht inteifere very seriously with the play of 

 even a skilful player. One of the principal results 

 obtained by M. Eesal is, that, during the instant of 

 impact, the direction of the friction is not constant. 

 The contrary was assumed by Coriolis. — (Comptes 

 rendus, Oct. 16, 1SS2. ) t. c. [756 



PHYSICS. 

 Acoustics. 

 Vibrations of membranes. — A. Elsas has stud- 

 led the vibrations of both square and circular mem- 

 branes, exciting them by connecting the middle of 



the membrane with a tuning-fork by means of 

 thread, attaching the thread to the membrane with 

 sealing-wax. The nodes and loops were determined 

 in the usual manner by the use of sand and lycopo- 

 dium powder. Thirty different forks were used, and 

 a great variety of membranes. The sound-figures 

 showed a gradual change from one mode of vibration 

 to another as the pitch of the fork was changed, 

 thus verifying the results of Savart. — (Beibl. arm. 

 phys. chem., "Mo. 2, 1SS3.) c. K. c. [757 



Photography of sound-vibrations. — BoUzmann 

 has studied the vibrations of a plate actuated by the 

 voice, using a method similar in many respects to 

 that employed several years ago by Prof. Blake of 

 Providence. A thin platinum plate was attached 

 Iterpendicularly to the iron plate; and, by an applica- 

 tion of the principle of the photophone, it was shown 

 to vibrate in the same manner as the iron plate. By 

 means of a solar microscope, an image of the shadow 

 of the platinum plate was thrown upon a screen, the 

 straight bounding-line of the shadow being condensed 

 by a cylindrical lens. The screen was then replaced 

 by a sensitized plate, moved rapidly at right angles to 

 the line of light produced by the cylindrical lens, while 

 the iron plate was made to vibrate by the voice. The 

 bounding-line between light and shadow on the plate 

 formed a curve whose nature varied according to the 

 sound uttered. The curves due to the vowels are 

 simple; those due to consonants, much more complex. 

 — [Phil, mag., Feb.) c. K. c. [758 



Optics. 



Conditions of sight which affect accurate 

 shooting. — Formerly the sight of a soldier as re- 

 gards shooting was a matter of little consideration; 

 but with the introduction of the Martini-Henry and 

 other rifles, which are accurate at 1,.500 yai'ds, sound . 

 eyesight becomes an important element. Dr. Litton 

 Forbes, surgeon-m.ajor in the Servian war, discusses 

 the varioiis changes taking place in the eye by M'liich 

 the sight is affected, and pi'oposes to correct defective 

 vision by means of a stenopaeic sight-adjuster. This 

 consists of a disk of colored glass, perforated with a 

 pin-hole aperture, having a correcting-lens of color- 

 less glass cemented to its back. The whole is to be 

 worn in a spectacle-frame. — [Journ. roy. united ser- 

 vice inst, no. 118, 1SS2.) c. E. m. [759 



A new optical phenomenon. — Axenfeld de- 

 scribes the conditions of an experiment in which 

 straight lines, a little on the near or far side of the 



