3 06 SCIENTIFIC RECORD FOR 1884 



347. K. Schering, of Gottiugen, describes a new instrument for de- 

 termining the variations of the vertical component of terrestrial mag- 

 netic force. This has been used at GoEtingen in connection with the 

 International Polar Observations; it has an advantage in that it is en- 

 tirely free from the perturbing influences of friction ; is much less influ- 

 enced by the torsion of the susijension thread and by the effect of tem- 

 perature on the center of gravity of the needle, which consists of a 

 magnetized steel tube 300 millimeters long and 10 millimeters interior 

 diameter. {Z. 0. G. M., xix, p. 547.) 



348. A. L. von Tillo has collected together all possible data relative 

 to the geographical distribution and secular variation of the magnetic 

 declination and dip in European Russia. {Z. 0. G. M., xix, p. 550.) 



349. Dr. Guido Schenzl publishes in one volume the result of sixteen 

 years' labor on terrestrial magnetism in Hungary. The observations 

 extend from 1865 to 1879. All data are reduced to the normal station at 

 Munich, and the normal epoch, 1875.0. The charts show by isogonic 

 and other lines the general distribution of declination, dip, and inten 

 sity. [Z. 0. G. M., xvii, p. 248.) 



350. E. E. Blavier, of Paris, having organized a very careful system 

 of observations, publishes a study on earth currents, made in accordance 

 with the suggestions of the Electrical Conference held at Paris in 1881, 

 As director of the telegraphic administration of France, Blavier has 

 had extensive opportunities and has used them skillfully. He finds the 

 general direction of the line of maximum electro-motive force in France 

 from northwest to southeast inclined 5G° to the magnetic meridian. 

 {Kature, xxx, p. lOG.) 



351. Prof. H. Wild has contributed to the subject of earth currents 

 an important study upon those observed in his buried telegraph cables 

 in the neighborhood of the observatory of Pavlosk. The principal series 

 of observations jjreviously made were those by Lament, 1850, with lines 

 only 100 meters long; Airy, 1862, with lines 13 and 16 kilometers long; 

 Galli, 1880, lines 4 and meters long. [Lieutenant Ray, at Point Bar 

 row, 18S2, used four lines, each of about 300 meters length.] Professor 

 Wild used four lines, north, south, east, and west of the central mag- 

 netic observing station, which is itself underground. The lines of wire 

 were each 1 kilometer in length, and crossed each other at the ob- 

 servatory, where the galvanometer was established. He deduces the 

 following results : 



1. In this neighborhood in seasons of magnetic calm the earth current 

 is so feeble that its difference of potential for one kilometer is less than 

 the uncertainty of our measurements, or 0.001 of the electro-motive 

 force of one Daniell's cell. 



2. The currents observed by Galli at Velletri, on his short line, were 

 wholly due to the ground plates ; those obsej-ved by Lamont were partly 

 ground-plate and partly terrestrial currents; and those observed by 



