PHYSICS, PROGRESS OF, IN 1902. 



555 



inum electrodes, there may be produced an in- 

 termittent discharge with a sound, audible in a 

 telephone. The pitch of the sound increases on^ 

 diminishing the resistance, on increasing the' 

 number of accumulators in the battery, on di- 

 minishing the capacity of the condenser, on di- 

 minishing the distance between the electrodes in 

 the tube, and on diminishing the pressure of air 

 in the tube. A Bunsen flame will act like the 

 tube if it be rendered conductive by salt vapor. 

 The period of electric oscillations in the condenser 

 circuit was far less than that of the sonorous 

 oscillations. Certain pitches of sound seemed 

 possible, others not, so that there were sudden 

 transitions from one pitch to another; and in 

 other cases the sound would not start sponta- 

 neously. J. Trowbridge (Scientific American, 

 April 5) concludes from experiment that light- 

 ning never strikes the surface of the sea. When 

 it seems to do so, the effect is an illusion of 

 perspective. The author has endeavored to pass 

 powerful sparks to the surface of water, in order 

 to obtain a strong spectrum of water vapor, but 

 in every case the sparks 6 inches in length, and 

 resembling lightning discharges as far as possible 

 refused to strike the level surface of the water 

 and passed to the edges of the containing vessel. 

 He also found it difficult to pass powerful sparks 

 from one stream of water to another, and prob- 

 ably lightning discharges do not pass through 

 regions of heavy rainfall. To produce a spark 

 under distilled Avater, it is necessary to use plat- 

 inum wires sealed in glass tubes all but about 

 half an inch. If these terminals are only dipped 

 to a small depth in the water, a spark passes 

 giving a very brilliant light resembling that of 

 an enclosed arc-lamp, but having no lines in 

 its spectrum. This spectrum is probably due to 

 water vapor, and the different spectra of light- 

 ning seem to be due to different amounts of water 

 vapor in the air. 



Alternating Currents. R. Weber (Annalen der 

 Physik, November, 1901) utilizes manometric 

 flames for studying changes in wave-form in alter- 

 nating currents. In the center of the membrane 

 of the chamber through which the gas passes 

 on its way to the burner he places a short soft- 

 iron cylinder in front of the laminated core of an 

 electromagnet, and the core is polarized -by being 

 placed in contact with one end of a permanent 

 bar magnet. The method does not give the ac- 

 tual wave shape, but changes in the wave shape 

 may by its aid be rendered visible. Specimens 

 are given of several flame pictures corresponding 

 different wave shapes. 



Electric Convection. Fitzgerald has suggested 

 that a charged condenser moving edgewise 

 through the ether should possess a magnetic field 

 between the plates, in consequence of the motion. 

 If, therefore, the earth is so moving, a condenser 

 placed with its plates edgeways to the direction 

 of the relative motion should experience a drag 

 during charge and a forward impulse during dis- 

 charge. Experiments made by F. T. Trouton 

 (Dublin Royal Society, April) with a delicately 

 suspended condenser gave only negative results. 

 Cremieu (Annales de Chimie et Physique, Novem- 

 ber, 1901) has obtained results that strengthen 

 the doubt already thrown on the existence of the 

 electric field due to magnetic variations, and also 

 upon the magnetic effect of electric convection. 

 In a repetition of Prof. Rowland's work, with 

 elimination of certain causes of error, the^result 

 was entirely negative. Rowland's and Him- 

 stedt's deviations are not due to a magnetic 

 field produced by electric convection, but ap- 

 parently to purely electrostatic causes. A 



charged body in a field of magnetic varia- 

 tions is not subjected to any ponderomotive 

 force, and a rotating disk does not produce, when 

 its charge is varied, the effects of induction that 

 a corresponding current subject to variations of 

 the same order would produce. The same rota- 

 ting disk charged in a constant manner does not 

 produce the magnetic field of a conduction cur- 

 rent carrying the same quantity of electricity. 

 A. Righi (Nuovo Cimento, October, 1901) asserts 

 that of the following four analogous phenomena, 

 following on electromagnetic theory, none have 

 yet been definitely verified by experiment: " (1) 

 An electric charge in motion should produce a 

 magnetic field. (2) A varying magnetic field 

 should produce an electric field. (3) A magnetic 

 pole in motion should produce an electric field. 

 (4) A varying electric field should produce a mag- 

 netic field." Attempts have been made to verify 

 the first two phenomena, but the last two have 

 not yet been experimentally tested. The author 

 reviews critically the various experiments made 

 to test the truth of these supposed laws, and 

 maintains that the second and third offer fewer 

 difficulties than the first and fourth. He points 

 out that the verification of any one entails the 

 truth of all four. 



Electrolysis. E. Wilson (Electrician, April 18) 

 has investigated the electrolytical effect of alter- 

 nate currents, which, as such currents are em- 

 ployed in rail-returns for electric traction, has 

 become of practical importance, especially in the 

 case of lead. He finds that the diminution in 

 weight is nearly twice as great at a low as at 

 a high frequency, which shows that frequency 

 plays an important part in the reaction. The 

 effect is entirely due to the current, as plates 

 immersed in the same electrolyte when no current 

 is passing are only slightly discolored. R. Lo- 

 renz (Electro-Chemist, December, 1901) explains 

 various phenomena of electrolysis in fused salts 

 by an empirical formula which he also deduces 

 from the first law of thermodynamics. Accord- 

 ing to this the counter-electromotive force in 

 the electrolytic bath is proportional to the cur- 

 rent yield. This is applicable to the commercial 

 electrolytic production of potassium, sodium, and 

 magnesium, and to the Heroult cell for the pro- 

 duction of aluminum. It explains the increased 

 yield obtained by cooling the cathode, and by 

 adding certain substances; in both cases the 

 solubility of the metal and the tendency to form 

 the so-called " fog " are diminished, the polariza- 

 tion is diminished, and the current yield conse- 

 quently increased. Diffusion of metal in the 

 form of " fog " explains the results of electrolysis 

 with diaphragms, through many of which the 

 metal " fogs " are unable to pass. 



Hall Effect. H. A. Wilson (Cambridge Philo- 

 sophical Society Proceedings, February) finds a 

 very large Hall effect in the ordinary electric dis- 

 charge in gases at low pressures, the electrodes 

 being immersed in an apparently uniform positive 

 column. The magnetic field always produces a 

 transverse motion of the column, as if it were 

 a flexible conductor carrying a current, and it 

 becomes brighter along one side of the tube. The 

 effect is proportional to the magnetic field, is 

 probably nearly independent of the current at 

 pressures down to 0.26 millimeter, and varies in- 

 versely as the pressure. The difference between 

 the velocities of the negative and positive ions in 

 the positive column is 4.95 X 10 s ! p, where p is the 

 pressure in millimeters of mercury. E. van Ever- 

 dingen, Jr. (Archives Nerlandaises, 4, 1901), ex- 

 plains the dissymmetry of Hall's effect as due 

 to a difference in the increase of resistance in 



