144 Intelligence and Miscellaneous Articles. 



(3) The conclusion has been arrived at that the electricity issuing 

 from an ignited platinum wire does not give a static charge to the 

 air itself, but that the charges observed as atmospheric electricity 

 have their seat in the particles already repelled iuto the air. 



(4) It is accordingly highly probable that atmospheric air, and 

 no doubt other gases also, cannot be statically electrified. 



(5) A fresh experiment is given which shows that, at ordinary 

 temperatures, negative electricity of high potential issues more 

 readily into the an* than positive. — Wiedemann's Annalen, No. 7, 

 1887. 



ON AN EXPERIMENTAL DETERMINATION OF THE WORK OF MAG- 

 NETIZATION. BY A. WASSMUTH AND G. A. SCHILLING. 

 If soft iron is brought from a very great distance near a magnet, 

 and thereupon so rapidly removed that the magnetism does not 

 dimmish, more work (W) is consumed in the removal than was 

 gained in the approach ; for in the removal the attraction is 

 stronger. The difference, A=W — L, is the work of magnetiza- 

 tion. It is assumed that the magnetizing force x acts on all parts 

 of the body used, an elongated ellipsoid of rotation, with equal 

 force in the direction of the axis of rotation. The work of mag- 

 netization is calculated for 1 cubic millim., if the moment of the 

 cubic millimetre is p. Wis then =x/j., and I>=\ pdx, as is shown 

 by calculation and by the experiments. Hence 



A=Xjjl—\ jidx— \ xdfi. 



In the experiments the iron ellipsoid, with its axis of rotation, 

 was in the same vertical plane as the limbs of a large electromagnet 

 provided with large pole-pieces, so that the field was as uniform as 

 possible; it was suspended to a balance, so that the attraction 

 p at various vertical distances z from the tips of the magnet-ends 

 could be determined. The surface of the curve whose abscissae 

 correspond to z, and the ordinates to p, delines the variation of 

 work, which according to theory must be equal to j fx dx. The 

 forces x and ft were measured by the currents induced in a fixed 

 coil, on changing the polarity, in one case with, and in another case 

 without, the freely-suspended iron core ; and the currents were 

 reduced to absolute measure by a terrestrial inductor introduced 

 into the circuit. Experiment confirmed the theoretical antici- 

 pations. They prove that the work for the change of position of 

 the iron is equal to the corresponding increase and decrease of 

 \ /u dx ; the work of magnetization is thus equal to the change of 



\ x dfx. Only in case, when li is proportional to x, do x djj. and \ ji dx 



give the same value, ^Xfx. The work is in that case proportional to 

 x 2 , on which may be based a method of determining x. — Wiener 

 Berichte, xciv. (i886); Beibldtter der Phi/sik, JS T o. 4 (1887). 



