DEPARTMENT OF TERRESTRIAL MAGNETISM. 319 



Tte observatory was completed and the magnetic variometers installed by- 

 January 1, 1919. The absolute instruments and the registering instruments 

 are described in detail. 



Magnetic storm of December 15, 1919, as recorded at the Watheroo Magnetic Observatory. 

 E. Kidson. Terr. Mag., vol. 25, 14-15 (March 1920). 



Magnetic distm-bances, earthquake records, and aurora at the Watheroo Magnetic Ob- 

 servatory, March 1920. E. Kidson. Terr. Mag., vol. 25, 61-62 (June 1920). 



These two communications give in detail the times of beginning and end- 

 ing, with approximate ranges, for the three magnetic elements as recorded 

 at the Watheroo Magnetic Observatory for the magnetic storms of December 

 14, 1919, March 4 to 5, March 14 to 15, and March 22 to 23, 1920. The 

 most severe of these storms was that on March 22 to 23. The notes accom- 

 panying aurora and earth-current disturbances affecting the telegraphic ser- 

 vice in Austraha are given. Particulars concerning earthquake records made 

 on the magnetograms of the observatory are given for such records on May 6, 

 August 29, September 1, 1919, and February 2, 1920. 



Earthquakes recorded at Watheroo Observatory, May 1920. E. Kidson. Terr. Mag. 

 vol. 25, 142 (Sept. 1920). 



This article gives particulars with reference to the earthquakes of May 11 

 and 13, 1920, recorded on the magnetograph of the Watheroo Magnetic 

 Observatory. 



Comments on Dechevrens's Electric Tide Observations. S. J. Mauchly. Terr. Mag., 

 vol. 24, p. 179 (Dec. 1919). 



In a brief note the author points out that neither of Father Dechevrens's 

 letters appearing in the Journal of Terrestrial Magnetism for December 1919 

 (pp. 175 and 178, respectively) contains evidence which enables one to decide 

 whether the currents observed by him at Jersey^ are of electromagnetic or 

 electrolytic origin. Observations were also suggested, the results of which, 

 it is believed, would shed some light on the origin of the currents in question. 



Results of Atmospheric-Electric Observations made during the Solar Eclipse of May 29, 

 1919. S. J. Mauchly and Andrew Thomson. Terr. Mag. vol. 25, 41-48, 

 (1920). (Abstract) Phys. Rev., vol. 15, 525-526 (1920). (Abstract of paper 

 presented before the American Physical Society, Washington, April 23, 1920). 



This paper is based upon observations made at Sobral in northeastern 

 Brazil in accordance with the general plan of the Department of Terrestrial 

 Magnetism for magnetic and electric observations during the solar eclipse 

 of May 29, 1919. 



Sobral (long. 40° 20'.8 W., lat. 3° 41'. 6 S.) is located in the belt of totality, 

 about 90 km. from the coast, and has an elevation of less than 100 meters. 

 The ecUpse, at Sobral, began at SH"" L. M. T. (lOHS"" G. M. T.) and ended 

 at 10^7"" L. M. T. (13»^29'° G. M. T.). The duration of totality was 5.3 

 minutes, mid-totality occurring at 9^19°^ L. M. T. (12^^00°^ G. M. T., civil). 



The atmospheric-electric elements under observation consisted of positive 

 conductivity, negative conductivity, and potential gradient. The apparatus 

 and methods used were in general the same as those employed by the authors 

 at Lakin, Kansas, during the solar eclipse of June 8, 1919^ except that the 

 potential-gradient observations during the eclipse were made at intervals of 

 one-half minute, instead of 2 minutes as at Lakin, and that a special form of 



iSee also: M. Dechevrens, Terr. Mag., vol. 23, pp. 37-39, 1918; Terr. Mag., vol. 23, pp. 145- 

 147, 1918; Comptes Rendus, vol. 167, pp. 552-555, 1918; Terr. Mag., vol. 24, pp. 33-38, 1919. 

 E. G. Bilham, Proc. Roy. Soc, vol. 94, pp. 165-181, 1918; Proc. Roy Soc, vol. 94, pp. 476-478. 

 1918; Q. J. R. Meteor. Soc, vol. 44, pp. 171-189, 1918. S. J. Mauchly, Terr. Mag., vol. 24, p. 

 100. June 1919. 



^Terr. Mag., vol. 24, March and June'l919. 



