February 5, 1904.] 



SCIENCE. 



203 



giving a displacement of three bands (that 

 is, a difference in phase of 1080°) corre- 

 sponded to a difference of 1101° calculated. 



Hertzian Waves since Hertz: A. D. Cole, 



Ohio State University. 



Hertz's experimental proof of the exist- 

 ence of electromagnetic radiation in 1888 

 was the culmination of Maxwell 's work and 

 led to a large output of new research. In 

 this Germany took the lead. Arons, Lecher, 

 Boltzmann and Zehnder introduced better 

 methods of showing the electrical Avaves. 

 The coherer came in 1895, although its 

 principle was discovered by Branly in 1891. 

 Three of the new receivers were strictly 

 quantitative; the electrometer of Bjerknes, 

 the oscillation-bolometer of Paalzow and 

 Rubens and the thermo-receiver of Klemen- 

 cic. Important improvements in the exciter 

 were made by Righi in 1893 and by Blond- 

 lot. J. J. Thomson and Lecher used the 

 Hertzian oscillations to measure dielectric 

 constants. Rubens and Arons showed that 

 the Maxwellian relation between these and 

 the refractive index held better with Hertz- 

 ian than with light waves. Cohn extended 

 this to the case of water. This was shown 

 to be rigidly true by Drude, by Cole and by 

 Cohn and Zeeman. Cole showed that 

 alcohol possesses anomalous dispersion for 

 electrical waves. Drude and Lampa proved 

 this true of many substances. Drude per- 

 fected apparatus for determining refractive 

 indices. Lecher and also Larasin and de 

 la Rive showed that the velocity along wires 

 is the same as in air. Blondlot, Trowbridge 

 and Duane, and Saunders gave more exact 

 proofs that this velocity was that of light. 

 The gap between the wave-lengths of 

 electrical and light waves has been nar- 

 rowed from each side. Lebedew reduced 

 the former to 1 mm., Dubois and Rubens 

 produced longer infra-red waves. 



The essentials of the electromagTietic 

 theory have been established. It remains 



to correlate with it our views of corpuscles 

 and the Becquerel rays. 



A Simple Alternate Current Frequency 

 Recorder: E. S. Johonnott, Rose Poly- 

 technic Institute. 



The instrument may be attached directly 

 to alternating current mains and a record 

 of the frequency obtained. To one pole 

 of the electromagnet of an ordinary electric 

 bell is attached a light armature which is 

 held at some little distance from the other 

 pole by a stiff flat spring. If now an 

 alternating current is sent through the 

 coils the armature vibrates, ordinarily, with 

 a frequency equal to twice that of the cur- 

 rent. If a stylus be arranged on the outer 

 end of the armature to leave a trace on a 

 smoked drum alongside that of a seconds 

 pendulum or an electromagnetic tuning 

 fork the frequency may be counted off at 

 once. The current through two incandes- 

 cent lamps in parallel in 100 volts is suffi- 

 cient to give ample motion. 



Iron Losses in Loaded Transformers: B. 

 S. Johonnott, Rose Polytechnic Insti- 

 tute. 



With the addition of a differential coil 

 to the Rayleigh phasemeter it was adapted 

 to measure directly the loss of energy in 

 the iron of a loaded transformer. The 

 readings give at once also the magnitude 

 of the exciting current and its phase with 

 respect to the induction. A transformer 

 of special design to test the effect of mag- 

 netic leakage was used in the experiments. 

 The conclusions drawn from the work were 

 as follows: (1) In a transformer having 

 great magnetic leakage between the prim- 

 ary and secondary, and in which a constant 

 induced B.M.F. is maintained and meas- 

 ured, {a) In the secondary. There is 

 an apparent increase in values of the loss 

 of energy in the iron, the magnitude of the 

 exciting current and the cosine of the angle 



