PHYSICS, PROGRESS OF, IN 1001. 



531 



uids it is assumed that the reverse is the case. 

 The solid will therefore begin to disintegrate into 

 the liquid, but the process stops before true solu- 

 tion sets in, and to account for this the author 

 assumes that the molecular adhesion between the 

 liquid and solid is greater than the molecular co- 

 hesion of the colloid, and that for the latter the 

 intermolecular attractive forces fall off more rap- 

 idly with increasing distance than for the for- 

 mer. Hence there exists a critical thickness of 

 the colloidal substance such that the forces de- 

 fined above just balance, and when this state is 

 reached disintegration ceases. 



Crystallization. W. Campbell (London Phys- 

 ical Society Proceedings, 17, pp. 337, 338) finds 

 that pressure may bring about crystallization in 

 solid metals. When a button of slowly cooled tin 

 is hammered it assumes a fine crystalline struc- 

 ture, and a similar crystallization is brought 

 about on the faces of a saw-cut or in filing. A 

 copper-tin alloy containing 1 per cent, of copper 

 gives the same effects as pure tin. The crystalli- 

 zation is only on the surface, as is shown by pol- 

 ishing, when the crystals slowly disappear, giving 

 place to the ordinary structure. G. Tammann 

 (Annalen der Physik, March) throws doubt on 

 the " liquid crystals " whose existence was in- 

 ferred by Lehmairn-from the fact that crystals 

 of certain substances, although perfectly clear in 

 the solid state, give rise when melted to turbid 

 liquids that appear bright when viewed between 

 crossed nicols. The author rejects the view that 

 such compounds retain their crystalline structure 

 in the liquid state, and considers the turbid liq- 

 uids as emulsions of a brown reduction product. 

 He points out that mixtures of powdered glass 

 and water, and other turbid non-crystalline 

 media, give a bright field between crossed nicols. 

 The author's theory does not explain the fact 

 that when such liquids are heated a sudden 

 change in their volume occurs at the point where 

 the turbidity disappears. 



Rigidity of Liquids. T. Schwedoff (Interna- 

 tional Physical Congress at Paris, Report, 1, 

 1900) points out that solids show some of the 

 properties commonly ascribed to liquids, and vice 

 versa. He discusses the relation between, defor- 

 mation in liquids and internal friction, and ar- 

 rives at the following results: " (1) The viscosity 

 of a liquid depends on its modulus of rigidity, 

 on the limit of its spring, on the speed of relaxa- 

 tion, and on the speed of deformation. (2) The 

 viscosity of a liquid may vary with the speed of 

 deformation. (3) The change in viscosity is more 

 sensible as the limit of elasticity increases. (4) 

 When the rigidity can not be measured directly, 

 the liquid may nevertheless be very viscous, if the 

 speed of relaxation be small. (5) On the other 

 hand, a liquid may present great fluidity and yet 

 have a measurable modulus of rigidity if the 

 speed of relaxation be very great." 



Capillarity. G. van der Mensbrugghe (Inter- 

 national Physical Congress at Paris, Report, 1, 

 1900) concludes from various experimental proofs 

 of the great elasticity of liquids, both under com- 

 pression and under traction, that liquids can not 

 be regarded practically as incompressible, and that 

 a liquid can not have a uniform density at all 

 points in its substance. He thus believes that 

 superficial tangential tensions must exist in the 

 outer layer of the liquid, and that normal tension 

 must exist, giving rise to evaporation. The au- 

 thor deduces the law that in order that one liquid 

 may spread over the surface of another, it is suffi- 

 cient and necessary that the mutual action should 

 be greater than the tension of the two surfaces. 

 C. T. Knipp (Physical Review, September, 1900) 



has measured tho surfarr- t<-n vatr-r above 



100 C. by determining tin !'UM- ; , t<> lilt 



a partly submerged platinum i liiicul 



temperature was found to h 



pressure 205 atmospheres. Tin: i i,,,, 



decreased linearly with incrc;i-- i ' 



until near the critical tempera! m . 



to zero, very rapidly. (See also /v'/rr/ro^//,/// 



under ELECTRICITY, below.) 



Viscosity. Hauser (Annalen der Phy-ik, j 

 has studied the influence of pressure on l.h.- vi 

 cosity of water up to 500 atmospheres in the t(;m 

 perature range of 15-100, using a capillary-tube 

 method. He finds that up to 32 increase of pres- 

 sure diminishes the viscosity, and that in this 

 temperature region the effect of pressure dimin- 

 ishes with increasing temperature. In the neigh- 

 borhood of 32, increase of pressure up to 400 

 atmospheres has no effect on the vicosity coeffi- 

 cient, while above 32 the viscosity is increased 

 by an increase of pressure of the amount stated. 



Sound. Velocity in Hot Air. E. H. Stevens 

 (German Physical Society) has measured the ve- 

 locity of sound in hot air by means of a resonance 

 tube of porcelain closed at one end and heated 

 in a coal-stove. The velocity at 950 was found 

 to be G8G meters per second, instead of the theo- 

 retical value 701.8. From further experiments 

 with an electrically heated tube, it was found 

 that the divergence between theoretical and ac- 

 tual values increases with the temperature. At 

 1,000 the actual velocity is 700.3 instead of 716. 



" Speaking Flames." E. Ruhmer (Physikal- 

 ische Zeitschrift, Feb. 23) finds that flames other 

 than the electric arc will produce sound, relative- 

 ly weak, under the influence of 'periodic variations 

 of electric current. If a microphone circuit be 

 connected with the low voltage coil of a trans- 

 former, and the current in the secondary coil be 

 led to a Bunsen burner, through the flame, and 

 back through a strip of platinum foil in the 

 flame, the effect is well shown. Higher tones are 

 better transmitted than lower. The author uses 

 with success in reproducing speech loudly with 

 an arc-lamp a transformer with 2 times as many 

 windings in the secondary as in the primary. 

 With the Bunsen burner, since the resistances are 

 greater, the secondary coil must have a corre- 

 spondingly greater number of windings. 



Mechanical Effect of Sound-Waves. B. Davis 

 (American Journal of Science, September, 1900) 

 produces by means of stationary sound-waves a 

 continuous rotation of a kind of anemometer 

 wheel in which the cups are replaced by gelatin 

 capsules with flat bottoms, the whole being 

 mounted on a needle-point by means of a glass 

 pivot. The rate of revolution at any point of 

 an organ-pipe is nearly proportional to the ve- 

 locity of the vibrating air particles at that point. 

 According to Bernouilli, a gas in^ motion is virtu- 

 ally less dense than a gas at rest. The air in 

 each capsule cylinder is at rest, while that on the 

 outside of it is in motion. The kinetic energy 

 evolved is due to the difference of density on the 

 two sides of the closed end of the cylinder. 



Musical Intervals in Melody. G. Zambiasi 

 (Nuovo Cimento, July) has tested the assertion 

 of Cornu and Mercadier that the scale of 

 stringed instruments in unaccompanied melody 

 is a comma () sharper in the third, sixth, and 

 seventh of the scale than in harmony. After in- 

 vestigation with artists' voices and a phonauto- 

 graph the author finds the acoustic scale, not 

 sharpened by a comma, very closely adhered to. 

 with occasional exceptions in the sixth of the 

 scale; but even then only in cases in which it 

 seems to be felt that the fifth has, for the time, 



