PHYSICS, PROGRESS OF, IN 1001. 



537 



ceeded in observing the effect described by Row- 

 land, using the same method employed in Cre- 

 mieu's first experiment, having avoided certain 

 things that, according to him, vitiated Cremieu's 

 results. Cremieu, however (ibid., August), as- 

 serts the validity of his investigation and abides 

 by his results as announced. 



Photoelectricity. J. Zeleny (Physical Review, 

 June) has experimented on the influence of the 

 temperature of a body upon the rate at which 

 electricity is discharged from its surface by ultra- 

 violet light. From a platinum wire the negative 

 electricity is at first discharged more slowly as 

 the temperature is increased; but the rate of dis- 

 charge reaches a minimum and then increases as 

 far as the highest temperature used (about 700 

 C.). The rate also depends upon the previous 

 history of the wire, being much greater after the 

 wire has just fallen in temperature than when it 

 has just risen. An iron wire also descends at 

 hrst to a minimum rate of discharge, but the final 

 value is many times that for ordinary room tem- 

 perature. Heating the wire does not change the 

 inability of ultra-violet light to discharge positive 

 electricity, even though the wire is raised to a 

 temperature where the positive electricity is being 

 discharged on account of the heat alone. The 

 author concludes that the variations observed are 

 mostly due to changes at the metal surface, and 

 not in the gas between the electrodes. 



Electrocaplllarity. S. Lemstrom (Annalen der 

 Physik, July) describes experiments on the be- 

 havior of liquids in capillary tubes under the 

 influence of an electric discharge. He finds that 

 under the influence of an electric current passing 

 through a stratum of air, water rises along the 

 sides of the tube, and forms drops in the upper 

 end; but this phenomenon takes place only when 

 the metal point from which the discharge passes 

 to the tube is connected with the negative pole 

 of the machine. 



The writer believes that the phenomena de- 

 scribed may be related to the influence of elec- 

 tricity on plants. 



Hysteresis. Krogh and Rikli (Elektrotech- 

 nische Zeitschrift, Dec. 27, 1900) have investi- 

 gated the effect of wave-form on loss by hyster- 

 esis, and find that for a given maximum induc- 

 tion, a peaked electromotive force wave (and 

 therefore a flat-topped induction wave) corre- 

 sponds to a higher hysteresis loss. They remark 

 that the result might have been anticipated, since 

 with a flat-topped induction wave the changes in 

 the induction are more rapid except, of course, 

 near the maximum points. 



Electric Inertia. A. Schuster (Philosophical 

 Magazine, February) notes that in the immediate 

 neighborhood of an ion the magnetic field will 

 be many times greater than that calculated on 

 the supposition of continuous distribution, and 

 hence the total magnetic energy is underesti- 

 mated, and the flow of electricity will behave as 

 if it had inertia. In calculating the chances of 

 verifying this inertia experimentally, the author 

 finds that the effect would be much smaller than 

 the extreme limits of Hertz's experiments on elec- 

 tric inertia. In metals, therefore, no results need 

 be looked for, but in a bad conductor, like car- 

 bon, we might get within the limits to which 

 Hertz worked. In the case of liquids and gases, 

 the chances of experimental verification of in- 

 ertia are equally remote, but a clear proof of such 

 inertia may be looked for in the domain of lumi- 

 nous vibrations. 



Motion of an Electrified Particle. E. Riecke 

 (Physikalische Zeitschrift, Jan. 5) has investi- 

 gated the motion of an electrified particle of ion 



in a uniform magnetic field upon ., hi, ; .. uniform 

 electric field is superimposed. 'I !,< i<- iM ( ,f mialy- 

 sis shows that the particle move.- , H . ;) ey- 

 cloidal curve, whose axis is a juinihu L r.,,- 



erating curve is not a circle \>\\\. ; i, < ! ;; , Tim! 

 the arcs of the cycloid expand dun. 

 These results bear upon the catho-le plu-n 

 the changes in luminous layers under j,;,r. 

 influence, and the theory of the aurora. 



The WcJmelt Interrupter. Lampa (Sii/m 

 richte of the Vienna Academy of Sciences. lOf), 

 Ila) has sought to find the reason why a Welmeli. 

 interrupter is less efficient when the smaller elec- 

 trode is negative. Using a coherer circuit con- 

 taining a galvanometer, the author finds that the 

 effect upon the coherer under continued sparking 

 at the interrupter is very pronounced when the 

 smaller electrode is negative, but very small when 

 it is positive. The effect is apparently greatest 

 when the interrupter is working quietly, and least 

 when it is working violently. Variation of the 

 length of the smaller electrode showed that the 

 effect is in a measure a periodic function of this 

 length. The phenomenon seems to be a resonance 

 effect, depending upon the resistance, self-induc- 

 tion, and electrolytic capacity of the circuit at 

 the moment of interruption. It is to be noted 

 also that the resistance is smaller when the small 

 electrode is positive than when it is negative. A 

 rotating mirror shows that the spark is of shorter 

 duration when the small electrode is positive than 

 when it is negative. 



Instruments for Electric Measurement. 

 M. Aliamet (Bulletin of the International Elec- 

 trical Society, July-August and September-Oc- 

 tober, 1900, reported in Science Abstracts) de- 

 scribes new forms of instruments shown at the 

 Paris Exposition, as follow: 



Galvanometers. In the Broca astatic galva- 

 nometer there are two vertical needles, each with 

 a consequent pole at its center and of opposite po- 

 larity. The system is astatic, even when the 

 needles have different strengths. One pair of bob- 

 bins is fixed with its axis at the height of the 

 consequent poles, the end poles being outside the 

 bobbins. A ballistic d'Arsonval galvanometer has 

 a moving coil, of 500 ohms resistance, very long 

 in a horizontal direction so as to increase the mo- 

 ment of inertia. The suspension consists of three 

 metallic wires attached to the galvanometer in a 

 plane containing its center of gravity. To avoid 

 swinging, vanes dipping in oil are attached to 

 the bottom. A registering d'Arsonval galvanome- 

 ter has six horizontal circular magnets, and the 

 moving coil carries a flexible arm with a pen 

 which is pressed against the registering drum 

 by an electromagnet. A portable mirror gal- 

 vanometer carries on one tripod a scale and 

 telescope supported on an arm that is jointed in 

 the middle of its length. In Callendar's register- 

 ing galvanometer a deflection closes one of two 

 relay circuits and releases a clockwork mechan- 

 ism, which moves a carriage with registering pen 

 along the slide wire of a Wheatstone bridge until 

 balance is obtained. 



Ammeters and Voltmeters. The Caron alter- 

 nate-current ammeter consists of a pair of horse- 

 shoe electromagnets acting on a flat, oblong coil 

 which is pivoted at one end. The current which 

 is introduced through a transformer, with a single 

 turn in the primary and a high resistance sec- 

 ondary, causes the coil to move in its own plane 

 from one magnet toward the other. The volt- 

 meter is exactly similar, except that the magnets 

 are wound with German silver to diminish the 

 effect of their self-induction. Siemens and Halskc 

 showed a rotary field ammeter, constructed on the 



