712 



PHYSICS IN 1899. 



that hydrogen lines are pronounced in the spec- 

 trum of the Wehnelt spark. These do not inter- 

 fere, but rather serve as lines of reference when 

 metallic spectra are obtained, as may be done 

 in great intensity and purity by varying the metal 

 of the anode. E. Thomson (Electrical World, 

 New York, XXXIII, p. 334) states that the in- 

 terrupter furnishes a means of performing ex- 

 periments hitherto regarded as requiring alter- 

 nating currents, such as the repulsion o 

 and the rotation of disks. A coil of few turns 

 wound on a core of iron wire is used. 



Electric Arc. Merritt and Stewart (Physical 

 Review, VII, p. 129) find that vapors from the 

 carbon arc can discharge electrified bodies by 

 contact. They retain the power for ten seconds, 

 but lose it when passed between a charged and 

 an earthed conductor. 



Inductoscript.McClell&nd (Proceedings of the 

 Cambridge [England] Philosophical Society, IX, 

 p. 522) concludes that the formation of figures on 

 photographic plates by electric discharges is due 

 principally to the light of the discharge, and not 

 to direct chemical action. The radical difference 

 between positive and negative figures he ascribes 

 to the fact that the form of discharge in air is 

 in one case a brush and in the other a glow. 



Frequency Indicator. Zeuneck ( Wiedemann's 

 Annalen, July) describes a method of controlling 

 the frequency of an alternating current, in which 

 the cathode beam of a Braun tube is exposed to 

 a rotary field produced by the current. The end 

 of the beam describes a circle on a screen, which 

 is interrupted by a tuning fork twice every revo- 

 lution. When the frequency is constant the dots 

 thus produced are on the same diameter. 



National Electric Laboratory. Wolff (Ameri- 

 can Association) describes the progress that has 

 been made in providing this country with a na- 

 tional laboratory in which electrical apparatus 

 can be tested and standardized. In the office 

 of the United States Standard Weights and Meas- 

 ures facilities are now available for testing most 

 of the ordinary electrical apparatus. Many ob- 

 stacles have been surmounted, and the progress 

 is encouraging. 



Magnetism. Magnetization. Roget (Proceed- 

 ings of the Royal Society, LXIV, p. 150) has ex- 

 tended up to 700 his experiments on the effects 

 of prolonged heating on the magnetic properties 

 of iron. He finds that annealed material is more 

 liable to change and that annealing removes all 

 changes produced by prolonged heating. The 

 heating need not be continuous, and exposure to 

 air makes no difference. The final state was 

 found to be one of lower hysteresis the higher 

 the temperature. 



Permeability. Meyer (Wiedemann's Annalen, 

 June) has attempted to connect the magnetic per- 

 meability of the elements with their atomic 

 weight. In the periodic series the paramagnetic 

 elements are grouped in the center and the dia- 

 magnetic ones at the ends. The difficulty of ob- 

 taining the permeabilities of the rare elements 

 interferes somewhat with the author's attempt. 

 (See also the following paragraph.) 



Low - temperature Phenomena. Osmond 

 (Comptes Rendus, CXXVIII, p. 1395) finds that 

 certain nickel and manganese steels show no mag- 

 netic properties till they have been exposed to 

 very low temperatures, the phenomenon being 

 analogous to the lowering of the freezing point 

 by dissolved substances. Some specimens have 

 their transformation points lowered to such an 

 extent that they do not become magnetic even 

 at the temperature of liquid air. Claude (Paris 

 Academy of Sciences, Aug. 21) finds that the 



PHYSIOLOGY. 



hysteresis and permeability of iron are both prac- 

 tiVallv constant from 25 to 185 C., the per- 

 meability at 1H5 being only 2.5 per cent, less 

 than at 25. These results agree with those of 

 Thiessen (who carried his experiments only as far 

 as 80), but they are opposed to those of Dewar 

 and Fleming. 



Properties of Alloy*. The same alloys of iron 

 and nickel have both magnetic and nonmagnetic 

 forms. This is explained by 'Houllevigue (Jour* 

 nal de Physique, VIII, p. 89) on the hypothesis 

 that in one form an iron nucleus is comprc--' <l 

 by a nickel shell, while in the other the sin-Ms 

 are ruptured and the pressure relieved. In iron 

 pressure decreases the magnetic susceptibility, 

 while in nickel the same effect is produced by 

 traction. 



Diclectro-tnagnctic Medium. This name is gi\ n 

 by Boccara and Pandolfi (Nuovo Cimento, IX. p. 

 254) to a mixture of chemically pure impalpable 

 iron powder with paraffin, the powder being >u- 

 pended in the paraffin before cooling. The in<l na- 

 tivity of this mixture increases more and more 

 rapidly with the percentage of iron. 



Chani/c of Form. Nagaoka and Honda (Philo- 

 sophical Magazine, XLVI, p. 201) find that hydro 

 static pressure produces decrease of magnet i/a- 

 tion in iron, and that magnetization produce- in- 

 crease of volume. In nickel both phenomena are 

 the inverse of this, although the effect is smaller. 

 In moderate fields a lengthwise pull inev 

 magnetization in iron up to a critical value, alter 

 which it decreases to a point where it i- le-s 

 than in unstretched iron. Magnetization likeu i-e 

 produces increase of length up to a certain point, 

 after which the length diminishes. With niekel 

 tension first produces decrease of magnet i/.at ion. 

 and then gradual increase, but not to a value 

 greater than in the unstretched metal. Magneti- 

 zation produces continuous diminution of length 

 in this metal. 



Effect on Thermal Conductivity. Konla 

 (Comptes Rendus, CXXVIII, p. 418) find- that 

 the thermal conductivity of soft iron is de i 

 along the lines of magnetic force, although unaf- 

 fected normal to those lines. Theory indi 

 that the effect is proportional to the square of 

 the magnetic permeability. 



Effect on Roiling Point. Du Bois Proceedings 

 of the Berlin Physical Society, XVII. p. ll 

 shows theoretically that a liquid alter- it- bnil- 

 ing point in a magnetic field, the point rising for 

 a paramagnetic and falling for a diamagnetie 

 body. The change varies with the field ami the 

 susceptibility, and is inversely as the den-it y ami 

 the heat of vaporization. For water the change 

 in a field of 50,000 C. G. S. units would be yWcfow 

 degree. 



PHYSIOLOGY. Theory. Con Dieting views 

 prevail concerning the structure of cell proto- 

 plasm. Manj r authors regard it as being com- 

 posed of two substances, one of which i- a eon- 

 tractile net according to some, a relatively ri-i'l 

 framework according to others, or as free fila- 

 ments: others as built up of a more solid material 

 and of a more fluid material whieh inhabits 

 minute spaces or vacuoles hollowed out in the 

 former; others as a heterogeneous jelly holding 

 granules; while others deny the truth to all ihe-o 

 views, and hold that the living cell protoplasm 

 is homogeneous in so far that it does not mani- 

 fest the coarse structure which these theories 

 ascribe to it. Its peculiar and transcendent 

 qualities are, according to them, associated with 

 molecular and not molar structure. W. 15. 

 Hardy has endeavored to show that if we put 

 on one side the confusion which has arisen from 



