PHYSICS, PROGRESS OF, IN 1892. 



<1 increases in solubility, so that fusion or 

 va|Miri/.ntii'ii takes place, bringing about an un- 

 stable cnmlition of supereaturation, which disap- 

 pear^ ly crystallization in the interspaces. Thus 

 Bolidifical ion by regelation is similar to that which 

 lakes place in cements. 



/li/1/riiniftry. Henri Gilbault (Paris Academy 

 of Sciences, Jan. 11) has devised a condensation 

 hydrometer in which the dew forms on a thin 

 sheet of platinized glass, whose temperature can 

 be measured very accurately by observing the elec- 

 tric.il resistance of the metal. The dew point can 

 thus be found to within ^ of a degree. 



Constant Temperature. Henry Clew (" Philo- 

 sophical Magazine," January) obtains a very con- 

 stant temperature by passing an electric current 

 through fine wire coiled about a glass vessel in a 

 calorimeter. He has thus been enabled to main- 

 tain a temperature within T J T for forty minutes. 



Light. Spectroscopy. Prof. Michelson has 

 added greatly to the possibilities of spectroscopy 

 bv the invention of what he calls the " wave com- 

 piler," by which he observes spectra from direct 

 interference of two beams of light. The instru- 

 ment is essentially a piece of plane glass placed 

 so as to bisect a right angle made by two mirrors. 

 The rays so fall that they are partly reflected and 

 partly transmitted, and movement of one of the 

 mirrors parallel to itself causes interference of 

 the reflected with the transmitted beam with any 

 desired difference of phase. By means of this de- 

 vice many lines never heretofore resolved have 

 been found to be close doublets notably the two 

 components of the sodium line and it has been 

 discovered that the widths of the component lines 

 in the hydrogen spectrum decrease as the pres- 

 sure increases, but not without limit. G. J. 

 Stoney (" Nature," Sept. 29) explains the doub- 

 ling and multiplying of the gaseous lines by call- 

 ing attention to the fact that the gases are usu- 

 ally observed in Geissler's tubes, where the mo- 

 tions of the molecules must preponderate in some 

 directions, instead of being indefinitely in all di- 

 rections, as they would be in open space. The 

 employment of Geissler's tubes to obtain gaseous 

 spectra is commented upon also by E. Prings- 

 heim (Wiedemann's " Annalen," No. 3), who says 

 that owing to this fact there is no direct evidence 

 that mere increase in temperature makes gases 

 glow. Siemens has shown that oxygen, carbon 

 dioxide, nitrogen, and hydrogen do not glow even 

 at l,r>00C. He concludes : (1) No gaseous source 

 of light obeys Kirchhof's law. (2) Glowing gases 

 at a temperature below 150 (cold flames) can be 

 obtained. (3) Salts of sodium glow only by chem- 

 ical action. (4) There is no experimental or theo- 

 retical evidence that gases glow luminously by 

 rise of temperature. Schutze (" Zeitschrift flir 

 Ph ysikalische Chemie," February) has found thnt 

 with a displacement of absorption from the violet 

 to the red color changes take place in substances 

 (as viewed with the naked eye) as follows : Green- 

 ish yellow, yellow, orange, red, reddish violet, vio- 

 let, blue violet, blue, blue green. This he calls 

 lowering the tint. Atoms or atomic groups that 

 lower the tint he terms bathochromic ; those that 

 raise it. hypsochromic. Hydrocarbon radicals are 

 always bathochromic. The influence of an atom 

 or group increases with increased atomic mass. 

 The addition of hydrogen to a group always 

 raises the tint. C. Runge (" Nature," April 28) 



notes, in relation to the line spectra of the ele- 

 ments, that doublets and triplets can be arranged 

 in series which appear to be very regular, the os- 

 cillation-frequency of a series being represented 

 by the formula, A Bn~* Cn~ 4 . For two 

 elements chemically related the series are dis- 

 tinctly homologous in the appearance of the 

 lines and in the values of A, B, and C. With 

 increase of atomic weight the lines shift to the 

 less refrangible end of the spectrum. The doub- 

 lets and triplets in each group broaden as the 

 atomic weight increases. The absorption spectra 

 of copper sulphate, chloride, and nitrate have 

 been found by T. Ewan (" Philosophical Maga- 

 zine," April) to change on dilution. The spectra 

 tend toward identity in dilute solutions. The 

 experimenter concludes that the acid and the 

 base are associated in producing absorption in a 

 strong solution, but not in a dilute solution. 

 This accords with the hypothesis of electrolytic 

 dissociation, not with that of hydrolytic disso- 

 ciation, or that of molecular aggregation. Lire- 

 ing and Dewar (" Philosophical Magazine ") have 

 examined the spectrum of liquid oxygen in larger 

 quantities than ever before, observing it in tubes 

 3 to 6 inches long. They find bands at A and 

 B that are related as are the solar groups. The 

 refractive index at the boiling point (182 C.) 

 is found to be 1-2236 for the D line. Konig and 

 Ritter (Wiedemann's "Annalen," No. 3) find 

 that the brightness of spectrum colors varies 

 with their absolute intensities. For all observ- 

 ers, even the color blind, the curve for the values 

 of brightness was of almost the same form for 

 the darkest shades, having a maximum at 535 

 H H (thallium green). As the brightness increased 

 the maximum increased with trichromatic per- 

 sons, first slowly, then rapidly, then slowly again. 

 At the brightest shade it was at about 610 /*/*. 

 Green-blind persons gave the same results as the 

 normal, but with red-blind persons the maximum 

 moved at first toward the long wave lengths, re- 

 maining stationary at 570. C. Fery (Paris Acade- 

 my of Sciences, Dec. 28, 1891) has devised a spec- 

 trometer on the principle of annulling by a solid 

 prism of variable angle and constant refractive 

 index the deviation caused by a hollow prism of 

 constant angle, filled with the liquid to be ex- 

 perimented upon. This is effected by a prism- 

 shaped cavity in a double convex lens. The 

 angle of the lens considered as a prism is varied 

 by shifting it in a plane perpendicular to the 

 axis, and the amount of the shifting necessary 

 to correct the deviation of the ray measures the 

 index. B. W. Snow (Wiedemann's " Annalen," 

 No. 10) has investigated the red emission spectra 

 of the alkali metals by a modified bolometer and 

 a delicate galvanometer with one of Bpys's quartz 

 fibers. He examined sodium, potassium, rubid- 

 ium, lithium, and caesium, and found that the 

 two rarest are specially rich in infra-red lines. 



Polarization. Lord Rayleigh (" Philosophical 

 Magazine," January) finds that the deviations 

 from Fresnel's law as to the disappearance of 

 tin' reflected polarized ray at the polarizing angle 

 are due to impurities. Jamin's results were thus 

 vitiated ; the deviation in the case of reflection 

 from clean water was found to be not. much more 

 than TTj'inr of that given by him. Possibly if a 

 perfectly clean surface could be obtained there 

 would be no ellipticity at all. 



