284 Intelligence and Miscellaneous Articles. 



effect increases with the density and quantity of electricity which 

 passes through the tube. It decreases as the pressure and diameter 

 of the capillary tube increases. If the Geissler tube is filled with 

 hydrogen, the optical effect is less than in air, other things being 

 equal. 



These results agree with the experiments on' glow-lamps and 

 flames, in so far that the higher the temperature the higher in 

 general is the useful effect. — Beibldtter cler PhysiJc, vol. xiv. p. 538. 



OBSERVATIONS ON ATMOSPHERIC ELECTRICITY IN THE TROPICS. 

 BY PROF. F. EXNER. 



The present paper forms the conclusion of a former one which 

 appeared under the same title (Phil. Mag. vol. xxix. p. 520), and 

 gives a complete discussion of the measurements contained in the 

 latter. The connexion between fall of potential and vapour- 

 pressure, which the author found to exist in our regions, is also 

 fully confirmed for the tropics, so that we may now regard the 

 electrical constants of the earth as determined with great certainty. 

 The quantity of electricity which is found in a column of a square 

 centimetre base above the earth's surface is, including the charge 

 of the latter, — 0*0038 absolute electrostatic units. The total 

 charge Q of the earth is, Q= — 2x 10 16 in the same units, and its 

 potential V referred to a point in space is — 9 x 10 9 volt. A further 

 fact now fully established is that the sign of the normal fall of 

 potential in the tropics is the same as with us, that is positive. 

 Only few observations could be made as to the change of fall of 

 potential with height, yet this showed distinctly an increase as 

 required by theory. 



The daily period of atmospheric electricity is decidedly less pro- 

 nounced in the tropics than with us, which is probably connected 

 with the extraordinary constancy of the weather. On most days 

 maxima could not be observed. — Wiener Berichte, July 10, 1890. 



INVESTIGATION OF ELECTRICAL VIBRATIONS WITH THERMO- 

 ELEMENTS. BY DR. IGNATIUS KLEMENCIC. 



The author investigated Hertz's vibrations by the help of a 

 thermoelement soldered between the ends of the secondary in- 

 ductor. By using two such inductors, one of which served as 

 standard while the other was moved about in the space affected, it 

 was possible to measure the distribution- of energy in a ray pro- 

 ceeding from the primary mirror, and at right angles to it. The 

 factor of condensation of a secondary mirror was further measured 

 for two different pairs of primary conductors, and was found to be 

 7 for a pair made exactly according to Hertz's directions, and equal 

 to 2*7 for a pair twice as long. The mirrors were exactly of the 

 dimensions mentioned by Hertz. — Wiener Berichte, July 17, 1890. 



