156 Scientific Intelligence. 



applied to this proposition, it leads to the conclusion that a cur- 

 rent of displacement in the air exerts no magnetic action, and 

 consequently that the charging current of a condenser is an open 

 current from the magnetic point of view. This is in direct oppo- 

 sition to one of the fundamental principles of Maxwell's theory, 

 and choice has to be made between renouncing this theory or the 

 principle of action and reaction. — Comptes Bendus, Nov. 25, 

 1900 ; Nature, Dec. 5, 1901. j. T . 



10. Frequency-determination of slow Electrical Vibrations. — 

 K. E. F. Schmidt places a telephone opposite the end of a reso- 

 nance tube and pushes a metallic disc to and fro in the tube until 

 the sound of the telephone is reinforced. In this way he obtains 

 the wave-length of the note of the telephone. He gives a table 

 of readings to show the accuracy of the method. The determi- 

 nations of the position of the minima varied from each other 

 hardly more than one millimeter, w T hen the length of the wave 

 was 9*356 cm . He also used Kundt's dust figures, and obtained 

 remarkably sharp and beautiful figures. Another method con- 

 sisted in using a single straight filament in an incandescent lamp, 

 and setting a photographic plate suspended from a pendulum in 

 motion. The plate shows maxima and minima corresponding to 

 the frequency of the current feeding the lamp. — Ann. der Physik, 

 No. 1, 1902, pp. 225-231. j. t. 



1 1 . The Bearing of the vpicard an d downward Movemen t of A ir 

 on Atmospheric Electricity. — F. Linke dwells upon the fact that 

 if at any place an electrostatic potential A exists and a conduct- 

 ing body of capacity C is in equilibrium, a quantity of electricity 

 E A =C. A results. If we now bring this body to a place of poten- 

 tial B, then we should have a quantity of electricity E B = C. B 

 neglecting disturbing influence of the field : the difference E =C 

 (A-B) must become free, if no change takes place in capacity. 

 In an electrostatic field, like that of the earth, any change of a 

 body in the direction of the force lines must result in free elec- 

 tricity. The author finds in the rise and fall of charged clouds a 

 cause of lightning potential, which to his mind is far more plausi- 

 ble than theories of the friction of water on ice and condensation 

 on ions. — Ann. der BhysiA; No. 1, 1902, pp. 231-235. j. t. 



12. Notes on Quantitative Spectra of Beryllium ; by W. N. 

 Hartley.* — In a quantitative examination made in 1885 of all 

 the known methods of separating beryllium from aluminum and 

 from iron, the various precipitates obtained were dissolved and 

 diluted to a known volume corresponding with the amount of 

 bases in solution. 



The solutions were spectrographically examined, and the photo- 

 graphs compared with others taken from solutions containing 

 accurately weighed quantities of pure beryllia. The coil used 

 was capable of giving a 5-inch spark in air. In place of a Leyden 

 jar a pane of glass coated on each side with a square foot of tin- 



*Read before the Royal Society, Dec. 5, 1901; from an advanced proof 

 received from the author. 



