PHYSICS, PROGRESS OF, IN 1893. 



637 



bubbles in a tiil*> of water is a periodic function 

 of their si/,o. As the size increases, the speed at 

 first diminishes; then, after reaching u mini- 

 mum, it increases, uml so on. depending on the 

 diameter of the tube. The shape of the bubbles 

 changes at each mnxinuiin and minimum, simi- 

 larly to the breaking up of a liquid column 

 through surface tension. 



Mahility of Viscous Liquids. A. B. Basset 

 (London Royal Society, Nov. 1) has further in- 

 vestigated a' phenomenon studied by Prof. Os- 

 born Reynolds in 18S3 : When water flows from 

 a cistern through a long tube, and a stream of 

 colored liquid is made to flow within the water, 

 the colored stream shows no tendency to mix 

 with the water till the velocity attains a certain 

 critical value, when it breaks at a certain point. 

 As the velocity continues to increase, the break- 

 ing point moves up toward the point at which 

 the fluid enters the tube. Mr. Basset finds that 

 (1) the tendency to instability increases as the 

 velocity of the liquid, the radius of the tube, 

 and the coefficient of sliding friction increase, 

 but diminishes as the velocity increases, and 

 that (2) the tendency to instability increases as 

 the wave length of the disturbance increases. 

 Mr. Basset investigated also the influence of oil 

 films in calming waves. Since the viscosity of 

 olive oil in C. G. S. units is about 3'25, and that 

 of water 0'014, the case is practically that of a 

 highly viscous liquid in contact with a friction- 

 less one. The result of a mathematical investi- 

 gation is that the motion will be stable unless 

 the wave length of the disturbance lies between 

 ft- and # of a centimetre, which explains the ef- 

 fect satisfactorily. 



Oases. Resistance. Cailletet and Colardeau 

 (Paris Academy of Sciences, July 4), in experi- 

 ments carried on from the Eiffel Tower, find 

 that the resistance of the air to a falling body is 

 proportional to the area of the resisting surface, 

 and independent of its form. The resistance in- 

 creases rather more rapidly than the square of 

 the velocity. 



Barometry. J. Joly (Dublin Royal Society) 

 has constructed a barometer of mercury and 

 glycerin, a column of the latter 250 centimetres 

 long being weighted by 67 of the heavier liquid, 

 kept from descending to the bottom by a disk 

 that just fills the tube. 



Breath Figures. Papers on this subject were 

 read before the London Physical Society (June 

 24) by W. B. Cuft and Rev. P. J. Smith. The 

 best figures are to be obtained by alternating 

 two coins with two sheets of glass and then con- 

 necting the coins to the poles of an electric ma- 

 chine. After sparks have passed for two min- 

 utes the breath will bring out a perfect figure 

 of the coin on the glass. The microscope shows 

 that moisture is deposited over the whole sur- 

 face, but in drops of different sizes, thus pro- 

 ducing the effect. II. F. Croft has brought out 

 the figures by sifting red lead on the glass as 

 well as by breathing on it, and has thus pre- 

 served a figure for two years. 



Sound. Phonics of Auditorium*. Dr. 

 Ephraim Cutter (" American Journal of Science," 

 December) recommends that the keynote of 

 every auditorium be ascertained experimentally, 

 and posted where speakers can see it. This can 

 be done simply by singing the scale and observ- 



ing what note is most stronglv re-enforced. The 

 keynote of the Saratoga City Hall was thus 

 found in 1890 to be F. 



Vibrations of Strings. Menzel and Raps 

 (Wiedemann's "Annalen," No. 12, 1891) huve 

 studied these by the new method of photograph- 

 ing them by electric light on a revolving cyl- 

 inder. 



Velocity. L. Melde (ibid., No. 12, 1891) has 

 measured the velocity of sound in membranes by 

 observing the vibration of strips fastened at the 

 ends and rubbed in the middle. His results, in 

 metres per second, were : 



Cotton Btrinjf 1,280 



Silk grossrrain ribbon... 980 

 Waxed cloth 670 



Waxed paper 8,040 



Drawing paper 1 ,9fi5 



Satin ribbon 1,950 



Heuip string 1,720 



N. Hesebius ("Journal de Physique," Decem- 

 ber, 1891) has found that the velocity of sound 

 in porous and fibrous substances is less than that 

 in free air. For cotton, for wave lengths of 24 

 to 60 millimetres, it was 261 to 146 metres per 

 second. A hemisphere of 25 centimetres diame- 

 ter made of metal gauze filled with ebonite shav- 

 ings, acted like a plano-convex lens, concentrat- 

 ing the sound of a Gallon's whistle accurately. 



II cat. Calorimetry. Barker and Hartog 

 (British Association) have constructed a calorim- 

 eter on the principle of the Bunsen ice calorim- 

 eter, but using solid acetic acid. It is more 

 delicate than the Bunsen, and can be used at 

 ordinary temperatures. 



%7iermometry. H. L. Callender (London Royal 

 Society. Dec. 10) constructs a compensated air 

 thermometer by xising an ordinary differential 

 thermometer, one of whose bulbs is kept in melt- 

 ing ice. An auxiliary bulb with taps allows the 

 introduction of known weights of mercury to 

 equalize the pressure, and the weight of this 

 mercury thus measures the dilatation of the 

 air at constant pressure. Prof. Wiborgh (Inst. 

 of Engineers of Scotland, Dec. 22, 1891) has 

 constructed an air pyrometer on a somewhat 

 similar principle, measuring the temperature by 

 increase of pressure, keeping the volume con- 

 stant. His instrument is made in two forms, 

 resembling the mercury and aneroid barometers 

 respectively. H. Le Chatelier (Paris Academy 

 of Sciences, Feb. 1) measures high temperatures 

 by the intensity of the radiations from a py- 

 rometer of platinum or clay compared with 

 those from a standard lamp. 



Thermodynamics. H. M. Elder (London 

 Physical Society, March 11) treats the action of 

 light on silver chloride in photography as a 

 problem in thermodvnamics, regarding the pres- 

 sure of the liberated chlorine as a function of 

 the intensity of the light, just as the pressure of 

 a saturated vapor is a function of the tempera- 

 ture. Chlorine in the presence of silver chloride 

 and protoxide is thus the working substance in 

 a ' light engine." He enunciates a law analo- 

 gous to the second law of thermodynamics, as 

 follows : " Energy can not of itself pass from a 

 less bright to a brighter bodv." Peter Lebeden 

 (Wiedemann's " Annalen," No. 2V starting with 

 Maxwell's law of the pressure exerted by inci- 

 dent rays on absorptive bodies, calculates that 

 between two bodies at temperature 0, with radii 

 of 2 millimetres and density = 10, the repulsion 

 due to this cause would exactly balance the at- 



