306 CARNEGIE INSTITUTION OF WASHINGTON. 



Further observations are urged for determining whether or not vertical 

 currents exist in the Earth's crust; similarly, the need is emphasized for the 

 investigation of electric currents in the sea. 



Polar-light investigations are considered under the following heads: 



(1) Determination and study of physical characteristics and properties. 



(2) Time variations and geographic distribution. 



(3) Interrelations with terrestrial magnetism, atmospheric electricity, and solar 

 phenomena. 



For the proper study of the physical characteristics we shall have to look 

 mainly to Stormer, Vegard, and others who are properly located and equipped. 

 Such work, as in the case of earth-currents, is not well adapted to the efforts of 

 volunteers and casual observers. The case is somewhat more favorable as 

 regards spectroscopic observations, and here it seems desirable to enlist the 

 attention and effort of such observatories as are favorably located. 



As regards observations for determining the time variations and the dis- 

 tribution of aurorse, and the interrelations between aurorae and terrestrial 

 magnetism, terrestrial electricity, and solar phenomena, there apparently 

 exists a large amount of observational data in the meteorological bureaus of 

 various countries, especially in Canada, the United States, Australia, and New 

 Zealand, which could be used to considerable advantage. It should also be 

 possible to interest volunteer observers in favorable locations, especially at 

 observatories, to supply most helpful data for certain phases of the study of 

 polar lights. In this connection it is noted that one of the most important 

 conditions for successful work by cooperative volunteer observers is that they 

 may be given such assistance as will enable them to know, definitely, what is 

 wanted. 



Attention is directed to the importance of securing the cooperation of 

 observers in the Southern Hemisphere and the desirability of arranging all 

 suitable data in the form of a polar-light catalog. 



Earthquake records on the Eschenhagen magnetograms at the Watheroo Magnetic Observa- 

 tory, Western Australia, August 13 and 23, 1921. W. C. Parkinson. Terr. 

 Mag., vol. 26, 137 (December 1921). 



This article gives a brief account of earthquake effects recorded at the 

 Watheroo Magnetic Observatory, Western Australia, on August 13 and 23, 

 1921, together with notes of disturbances indicated on the Milne seismo- 

 grams at the Perth Observatory, communicated by Government Astronomer 

 H. B. Curlewis. 



Dynamic and tilting deviations. W. J. Peters. 



An investigation was begun by making an analysis of certain simultaneous 

 records obtained with the standard compass and the deflector on the subant- 

 arctic cruise of the Carnegie, harbor swings, and observations in the vicinity 

 of the magnetic equator. The analysis revealed small systematic discrep- 

 ancies and indicated the desirability of testing the instruments in a uniform 

 magnetic field on shore. They were accordingly mounted in the same rela- 

 tive positions at the Standardizing Magnetic Observatory, Washington, that 

 they have on board the Carnegie during a swing, in order to determine if any 

 part of the discrepancies were caused by the metal binnacles, bowls, or acces- 

 sories, or by any one instrument upon the other. The experiments were made 

 with the assistance of Mr. H. F. Johnston and showed satisfactorily that the 

 binnacle and accessories are practically free of iron and that there is no mutual 

 effect between the instruments. 



Experiments also were made with the standard compass on a harmonic- 

 motion table where the instrument may be given simple harmonic motion in 



