710 



PHYSICS, PROGRESS OF, IN 1890. 



sounds recorded by it with clearness, though 

 they are diminished in volume. 



When it is giving out a record of orchestra 

 music, the different instruments can be distinctly 

 heard, or soprano, bass, and tenor voices recog- 

 nized singing in unison. On account of the loss 

 of volume in sound, a second phonograph does 

 not successfully take its record from a first. 



The record as engraved on the wax surface of 

 a cylinder is called a phonogram, and Fig. 5 

 shows a magnified section of a cylinder with the 



s\ "-Hr^^SHSSSal'fflSB 



:::.r::v.;.;;;;;;S 



J)lhi inii 



FIG. 5. MAGNIFIED SECTION OF CYLINDER, WITH PHONO- 

 GRAM. 



phonogram of a piece of instrumental music. 

 The deep dents apparent on this are caused by 

 loud or sudden sounds. 



The principle of the phonograph has been ap- 

 plied to many ingenious uses. A tiny instru- 

 ment incased in the body of a doll and operated 

 by means of a crank at the back, repeats nursery 

 rhymes, sings songs, or makes speeches in a 

 shrill childish voice. Clocks are also made to 

 announce the hour in spoken words. As a stenog- 

 rapher, the phonograph already occupies a wide 

 field. One of its cylinders will hold from one 

 thousand to fourteen hundred words. Inclosed 

 in a case, a cylinder can readily be mailed to a 

 distant point, and placed under the needle there, 

 will repeat its message in the very tones of the 

 sender. 



The possible applications of this instrument 

 for recording sounds instead of written language 

 are numerous. Among them may be mentioned 

 the taking of evidence in court, the giving of the 

 correct pronunciation and accent of a foreign 

 language, and the furnishing of a means of com- 

 munication for the blind. 



PHYSICS, PROGRESS OF, IN 1890. 

 Constitution of Matter. Sir William Thom- 

 son (Edinburgh Royal Society, Feb. 3) gives 

 some new estimates of molecular distances. He 

 proves, by mathematical considerations, that the 

 ratio of the latent heat of vaporization of a 

 liquid to six times its surface tension gives ap- 

 proximately the number of molecules per lineal 

 unit. The results for several liquids are as follow : 



LIQUID. Molecules per lineal centimetre. 



Water 50,000,000 



Alcohol 52,000,000 



Kther 80,000,000 



Chloroform 15,000,000 



Carbon -bisulphide 19,000,000 



Turpentine 30.000,000 



Petroleum 40.000.000 



Wood spirit 70,000,000 



No dependence can be placed on the relative 

 values of the numbers. The noteworthy point is 

 their complete agreement in order of magnitude. 

 (See also Density, below.) 



Mechanics. Gravity. C. V. Boys, by using 

 the delicate quartz fibers that were first made by 

 him, has succeeded in showing the Cavendish ex- 

 periment on the attraction of two masses of lead, 

 in an ordinary room, with no protection against 

 draughts. His whole apparatus does not exceed 

 the size of an ordinary galvanometer, and he 

 uses a simple galvanometer lamp and scale. 

 With this the mutual attraction of two bird 

 shot can be shown ; whereas, with the most 

 delicate suspensory fibers hitherto known, the 

 attraction of large masses could be demonstrated 

 with great difficulty, and only by taking ex- 

 traordinary precautions. De Sparre (Paris Acad- 

 emy of Sciences, Oct. 6) has deduced a complete 

 formula for the motion of Foucault's pendulum 

 in air, which shows that the resistance of the at- 

 mosphere has an indirect influence on the veloc- 

 ity of rotation of the plane of oscillation, besides 

 diminishing the amplitude of the vibration, and 

 causing a deformation of the oscillation curve. 

 Dr. Lehmann, in a discussion of ancient Babylo- 

 nian weights and measures (Berlin Physical So- 

 ciety, Nov. 22), gave the opinion that the Babylo- 

 nians knew the length of the seconds pendulum. 

 At Babylon this is 992*5 millimetres, and the 

 Babylonian foot is almost exactly one third of 

 this length. 



Density. Dr. G. Johnstone Stoney ("Philo- 

 sophical Magazine," June) maintains that the 

 distinction between different parts which is im- 

 plied in the word "density" does not exist in 

 the elemental ether, and that in it the element 

 of volume is identical with the element of mass. 

 Assuming Thomson's vortex-atom theory of the 

 constitution of matter, the density of a lump of 

 iron, for instance, is nothing but a function of 

 the primary motions that prevail in a certain 

 portion of space, the '* matter " of the iron being 

 nothing but a tangle of vortex motions in the 

 ether. In the dynamics of the ultimate motions 

 of this ether there is no such physical quantity 

 as density. Only when an accumulation of these 

 primary motions is lumped together, and where 

 we investigate the drifting about of these accu- 

 mulations, do we find need of such a conception, 

 as a substitute for having to take separately into 

 consideration some of the motions that are really 

 going on. 



Elasticity. Prof. Richard Threfall, of Syd- 

 ney, Australia, has measured the elastic constants 

 of 'C. V. Boys's quartz threads. The results given 

 in C. G. S. units are as follow : 



Simple rigidity at 22 C 2 8815 x 10" 



Youngs modulus at 23 C 5 1785 x 10" 



Bulk modulus 1-435 x 10" 



Temperature coefficient of stiffness from '22 



to 98 C -000133 



Coefficient of lineal expansion from 80 to 3(i. . -0000017 



Corresponding temperature coefficient 



The limit of allowable twist was one third of a 

 turn per centimetre in a fiber -01 cm. in diam- 

 eter. Prof. John Perry ("Philosophical Maga- 

 zine," March) has investigated the behavior of 

 twisted strips of metal, which show curious 

 properties. A straight strip was first permanent- 

 ly twisted so as to leave the axis straight. When 

 force was applied to stretch such a strip there was 



