3G8 SCIENTIFIC RECORD FOR 1884. 



4. As soon as the earth currents in both lines become strong, the mag- 

 netic instruments deviate from their ordinary positions, and these per- 

 turbations increase with the strength of the earth currents, but not in 

 any regular proportion. 



5. The changes in the south-to north line preceded by about five min- 

 utes the changes in variation of declination, and similarly the current 

 in the east-to-west line preceded the changes in the horizontal intensity, 

 so that the earth current would appear as the primary cause. He con- 

 cludes that the earth currents are the primary cause of many pertur- 

 bations, but not the cause of the periodic variations in the magnetic 

 elements. [Z. 0. M. G., xix, p. 510.) 



353. Prof. K. Schering, of Gottingen, criticising Professor Wild's re- 

 sults, states that the method is not thoroughly reliable, and expresses 

 his conviction that we cannot determine a difit'erence of potential be- 

 tween two points of the earth, nor even i)rove its existence, if we use 

 ground plates which by contact with the earth become electrified in any 

 unknown manner. He recommends the method introduced by W. Sie- 

 mens in the programme of the German North Polar expedition for 1882- 

 '83 as the only one to be used in determining the currents induced by 

 the changes taking place in the magnetic force of the earth. {Z. 0. G. 

 M., XIX, p. 552.) 



354. The great magnetic storm and auroral display of November 17, 

 1882, is abundantly discussed, with numerous contributions of observa- 

 tions, throughout vols, xxvii and xxviii of Nature. 



355. T. W. Backhouse, of Sunderland, collects together all accessible 

 observations on the spectrum of the aurora, and shows that the number 

 of striking coincidences between it and the modified air spectrum make 

 the suggestion that they are identical one worthy of consideration. 

 [Nature, xxviii, p. 209.) 



356. O. Jesse discusses the auroral arc observed October 2, 1882, and 

 places it at an altitude of 122.2 kilometers, with a probable error of 4.5 

 kilometers. {Z. 0. G. M., xviii, p. 238.) 



357. O. Jesse, in some remarks on the determination of the altitude 

 and position of the aurora, states that the very rapid changes going on 

 during a display make it important to have a method of determining its 

 altitude by observations made at one place. He has, therefore, devel- 

 oped such a method, which is published in full in the Astronomische 

 Nachrichteu, No. 2540. This method is based upon the assumption that 

 the rays constituting the aurora lie on the surface of a cone whose apex 

 [s in the interior of the earth, where the direction of any one ray and the 

 osculating magnetic axis of the earth intersect each other. The appli- 

 cation of this method requires that we should measure for as many rays 

 as i)0ssible the angle under which the ray or its prolongation intersects 

 the horizon; also, the azimuth of the point in which the ray cuts the 

 horizon, together with an accurate determination of the time; further- 

 iiiore, for sojne of the rays the apparent position of their highest exten- 



