052 



PHYSICS, PROGRESS OF, IN 1894. 



Science, Oct. 1) shows that a crystallizing body 

 loses heat in essentially different ways, accord- 

 ing as it is adiathermanous or diathermanous. 

 A 11 substances become diathermanous below 70 

 C., hence the true temperature of crystalliza- 

 tion is obtained only by keeping the surrounding 

 medium slightly below the solidifying point. 

 This explains various anomalies, as in previous 

 determinations of the crystallization points of 

 chloroform, etc. Jtloore (" Zeitschrift fur Physi- 

 kalische Chemie, December, 1893) has measured 

 the velocity at which crystallization proceeds in 

 a supercooled substance, by following with the 

 eye the moving line of demarcation between 

 solid and liquid in a U-tube. With acetic acid 

 the velocity was found to be uniform at any tem- 

 perature and independent of the diameter of the 

 tube, and with this substance, phenol, and mix- 

 tures of phenol with water and phenol with cre- 

 sol, the velocity increases with the amount of 

 supercooling, but at a diminishing rate. For 

 phenol the velocity is 0'6 cm. a second with 4-4 

 supercooling, and 2*9 cm. with 15'8. The addi- 

 tion of water or cresol reduces both the velocity 

 and the rate of its increase. 



Cohesion. Kasterine (" Journal of the Rus- 

 sian Physico-chemical Society," xxv, p. 51), from 

 experiments on the variation of cohesion in 

 liquids, and on the assumption that the molecular 

 forces conform to Newton's law of the square of 

 the distance, derives the following laws : 1. The 

 product of the intensity of molecular action bv 

 the molecular weight is a constant. 2. For dif- 

 ferent liquids at corresponding temperatures the 

 radii of the spheres of molecular activity are ap- 

 proximately proportional to the square roots of 

 the molecular weights. 3. At corresponding 

 temperatures the physical molecule in different 

 liquids contains the same number of chemical 

 molecules. 



Density. Kohlrausch and Hallwachs (Wiede- 

 mann's " Annalen," October) have measured the 

 density of very dilute aqueous solutions to with- 

 in one millionth by weighing a glass globe sus- 

 pended in the solution by a fine fiber. Interest- 

 ing details regarding the molecular volumes of 

 the dissolved substances have thus been brought 

 out for instance, phosphoric and sulphuric acids 

 show a diminution of this volume at extreme di- 

 lutions. 



Capillarity. Quincke (British Association, 

 1894), as a result of researches occupying forty 

 years, finds that drops of oil floating on slightly 

 alkaline water are attracted toward the walls of 

 the vessel and then repelled, the spreading of the 

 soap film that results from the action of the al- 

 kali on the oil giving rise to periodic vortex mo- 

 tion. Viewed with the microscope the film shows 

 the same minute strings of pearly beadlike bub- 

 bles that are characteristic of protoplasm. 



Vixrnttity. Owen Glynn Jones (London Phys- 

 ical Society, Feb. 9) has measured the viscosity 

 of liquids by observing the velocity of small 

 drops of heavier liquids falling through them. 

 A water drop of 1 mm. radius was found to fall 

 1 inch an hour in castor oil at 8 C. This meth- 

 od has been criticised, the formulae used being 

 calculated originally for solid spheres, and the 

 critics holding that internal motion in the drops 

 as well as mutual contamination of the two 

 liquids would complicate matters. 



Hydrodynamics. Prof. Osborne Reynolds 

 (British Association, 1894) has studied the suc- 

 cessive stages in the motion of water passing un- 

 der gradually increasing pressure through a ver- 

 tical tube constricted in the middle. The water 

 first leaves the constriction as a narrow steadv 

 jet, then it fills the lower part while eddies ap- 

 pear below the constriction, then the motion be- 

 comes turbulent, and finally there is an appear- 

 ance as of air bubbles at the constriction with a 

 singing or hissing sound. 



Decomposition of Liquids by Pou-ders. Dr. 

 G. Gore (Birmingham Philosophical Society) 

 finds that when finely powdered substances, es- 

 pecially silica, are placed in a solution the adher- 

 ent film of liquid contains more than the normal 

 percentage of the dissolved substance. The 

 amount of the substance thus abstracted de- 

 pends on the kind of powder, its fineness, its 

 quantity in proportion to the dissolved sub- 

 stance, the absolute amount of the latter, and in 

 some degree on the temperature. The results 

 seem to throw light on the purification of water 

 by filtration. 



Gases. Condensation. In a lecture at the 

 Royal Institution, published in " Nature,'' Dec. 28, 

 Shelford Bidwell states his conclusion from his 

 own experiments, that the dense condensation of 

 steam produced under certain circumstances is 

 due neither to electrical action nor to dust nu- 

 clei, but probably to dissociated atoms of atmos- 

 pheric gases acting in some unexplained man- 

 ner. Carl Barus (' Nature," Feb. 15) objects to 

 Mr. Bidwell's conclusions, and is of the opinion 

 that condensation upon minute particles in the air 

 will account for all the observed phenomena. 



Critical Point. Kuenen (Amsterdam Acad- 

 emy, May 26) has carefully investigated abnor- 

 mal phenomena near the critical point, and con- 

 cludes that they are due to impurities. From a 

 repetition, for' instance, of Galitzine's experi- 

 ments, which have been supposed to show that 

 ether above the critical point has different densi- 

 ties, according to its having been entirely fluid 

 or partly vapor, Kuenen concludes that "Galit- 

 zine's results were due to a trace of some non- 

 coercible gas, perhaps air. 



Vortex Motions in Air. Quincke announced 

 in 1890 that two spheroids of a mixture of oil 

 and chloroform, falling simultaneously in 

 water, approached and receded alternately, ow- 

 ing to vortex motion in the water. He now 

 finds (Wiedemann's " Annalen," July) that the 

 same phenomenon occurs when two' soap bub- 

 bles filled with coal gas ascend together. Simi- 

 lar phenomena occur when small dust particles 

 fall in air, or liquid, or when a current strikes 

 particles at rest. 



Barometry. Bartrum has invented what he 

 calls an "open-scale barometer," which is de- 

 scribed in "Nature," March 22, p. 488. The 

 lower part resembles that of an ordinary mer- 

 cury barometer, but near the upper surface of 

 the mercury the tube is enlarged into a bulb, 

 above which it is again contracted. The bulb 

 is filled Avith a red fluid, the upper surface of 

 which gives the barometer reading, a small 

 change of level of the mercury causing a large 

 one in the fluid. An inch of mercury is repre- 

 sented on the scale by 9 inches, and it is claimed 

 that the atmospheric pressure may thus be ob- 





