Maech 19, 1909] 



SCIENCE 



469 



compressibility witli pressure seems somewhat less 



than has been supposed. 



An Experimental Determination of the Terminal 



Telocity of Fall of Small Spheres in Air: John 



Zelent and L. W. McKeehan, University of 



Minnesota. 



Stokes's formula for terminal velocity of fall 

 of a sphere in a viscous fluid expresses the result 

 in terms of the acceleration of gravity, the radius 

 of the sphere, the density of the sphere, the 

 density of the fluid and its viscosity. This for- 

 mula has been used by J. J. Thomson, H. A. 

 Wilson and others in the determination of the 

 charge carried by a gaseous ion. 



The velocity of fall of lycopodium, which satis- 

 fies Stokes's criterion that the sphere shall be 

 small, was determined experimentally. Variations 

 in the size and density of individual particles 

 were provided against by finding the time of fall, 

 in a wide tube, of a large number of particles in 

 each experiment. Tlie time of fall of the center 

 of gravity of the cloud of particles was assumed 

 to be that of a single particle of average radius 

 and density. The uniformity of the material 

 makes this admissible. 



The formula gives velocities, for this particular 

 size, 50 per cent, in excess of those observed. 

 Since this difference depends probably on the size 

 employed, the amount by which the charge on an 

 ion must be increased can not be stated until 

 further experiments are carried out with particles 

 of different sizes. 

 Note on the Effect of the Phase of Harmonics on 



SovMd Waves: M. G. Llotd and P. G. Aqnew, 



Bureau of Standards, Washington. 



A harmonic alternator set giving frequencies 

 from 60 to 900 was used to excite a telephone. 

 By choosing a fundamental from one machine and 

 a harmonic from another, and then driving the 

 two generators just out of synchronism, a con- 

 tinuous cyclic change of phase relation occurs. 

 Ordinarily the combined tone sounded by the tele- 

 phone changes periodically, but these changes are 

 really beats due to the interference of higher 

 harmonics common to the two sources. By con- 

 necting the generators three phase, star, and 

 choosing frequencies having a ratio of 3 to 1 or 

 9 to 1, common impurities are eliminated. When 

 so connected no change in the sound could be 

 detected at low intensities. With louder tones 

 there were cyclic changes which were believed to 

 be due to harmonies introduced by the telephone 

 itself, rather than to an actual dependence of 

 quality upon phase. 



Magnetic Double Refraction Normal to the Field 

 in Liquids: C. A. Skinnek, University of Ne- 

 braska. 



Fourteen different liquids were investigated, 

 including nitrobenzol, nitrotoluol, chlor-benzol, 

 brom-benzol, etc. Twelve of them showed electric 

 double refraction. Each was studied through the 

 spectrum from blue to red (440 to 660). The two 

 effects agree in the law of variation. In carbon 

 bisulphide alone were the electric and the mag- 

 netic /3 of opposite sign. 



The Absorption Spectra of Various Potassium, 



and XJranyl Salts: Haert C. Jones and W. W. 



Steong, Johns Hopkins University. 



The purpose of this investigation was to find 

 out the nature of the absorbers of the light rays 

 and the effects upon them of external conditions. 

 It is possible in the case of the uranium atom or 

 molecule to make a large number of changes that 

 affect its absorbing power. Salts like the nitrate, 

 sulphate, bromide, acetate and chloride of UOa 

 have been used. This gives the effect of the 

 chemical radical on the absorption. Different 

 solvents can be used and various concentrations 

 and the temperature varied. The solution can 

 be placed under great pressure or in a powerful 

 magnetic field. Dehydrating agents like alumin- 

 ium chloride and sulphuric aeid can be added. 

 Some or all of these changes are being made and 

 some interesting results have been found. 



A Rowland concave grating is used to give the 

 absorption spectra. Wratten and Wainwright red 

 sensitive films are used for the photographic work. 

 The work is being carried on by a grant from the 

 Carnegie Institution of Washington and is a con- 

 tinuation of the work of Jones and Anderson 

 (Publication No. 110, Carnegie Institution). 



Beer's law was found to hold for potassium 

 ehromate, potassium dichromate, potassium ferro- 

 cyanide and potassium ferricyanide. Concentrated 

 solutions of the uranyl salts do not obey Beer's 

 law. 



Uranyl salts show ten absorption bands in the 

 blue-green part of the spectrum. When aluminium 

 chloride is added to uranyl chloride these bands 

 are shifted towards the red. Calcium chloride acts 

 in the same way. Several new bands have been 

 found for the chloride (these are very narrow) 

 which none of the other uranyl salts have so far 

 been found to show. 



New Series in the Spectra of Ca, Sr and Ba: F. A. 

 Saundees, Syracuse University. 



