314 CARNEGIE INSTITUTION OF WASHINGTON. 



advantages. Eddy-current effects have been more thoroughly studied by 

 rotating copper and otherwise. The work is still in progress and other tests 

 remain to be appUed. 



The most extensive observations have been made on a rod of Norway iron 

 (for which observational curves were shown), many observations have been 

 made on a rod of cobalt, and some on rods of cold-rolled steel. All the 

 rods gave values near one-half of 7.1 instead of 7.1, just as in the experi- 

 ments on iron by the method of electromagnetic induction, thus again appar- 

 ently indicating an effect of positive electricity. Satisfactory experiments 

 on nickel have not yet been made. 



It is interesting to observe that, while all the sources of trouble have not 

 yet been removed, the method is so sensitive that, in the later part of the night, 

 when the extraneous magnetic disturbances are least, the effect can be meas- 

 ured at even very small speeds. Cui'ves between the scale readings for right 

 and left handed rotations and the time were exhibited, showing clearly the 

 effect for cobalt at the speed f revolution per second. 



The paper closed with a reference to recent experiments on the converse 

 effect (rotation by magnetization) . These experiments on the theory which 

 has been adopted by the investigators, but which involves an uncertain 

 assumption with reference to the seat of the reaction to the resultant electron 

 momentum produced on magnetization, also appear to indicate an effect of 

 positive electricity of the magnitude given above. 



Design and construction of a sine galvanometer for the precise determination of the hori- 

 zontal component of the Earth's magnetic intensity. S. J. Barnett. (See p. 307). 



The construction of the instrument briefly described in the annual report 

 for 1919 is now well advanced. The only modification of the design published 

 in 1919 consists in replacing the marble magnetometer-box and suspension 

 with air damping, by a copper box and suspension with electromagnetic 

 damping. This modification, in the interest of simpHcity, has been made 

 possible by the fact that copper can be cast free from iron in the foundry of 

 the Department of Terrestrial Magnetism. 



Procediu-e at the magnetic observatories of the Carnegie Institution of Washington. L. A, 

 Bauer. Terr. Mag., vol. 24, No. 4, 149-153 (Dec. 1919). 



Until some recommendation has been made by the International Section of 

 Terrestrial Magnetism and Electricity, it has been decided to adopt the fol- 

 lowing procedure at the magnetic observatories of the Department of Terres- 

 trial Magnetism: 



(1) At each observatory, the magnetograph tabulations will apply to the 

 local day corresponding to the nearest standard (15°) meridian. 



(2) In scaling magnetograms, the mean ordinate shall be taken as applying 

 to a 60-minute interval centering at the half-hour of the standard time 

 adopted. (Thus the first ordinate will be for the interval from 0** to I'' stand- 

 ard time.) 



Accordingly, at Watheroo (longitude, 7''44'" E.), the first mean ordinate 

 will be for the interval 0»>-l\ 120th M. T. East, or 16'^17'> G. M. T. of pre- 

 ceding day; for Huancayo (longitude, 5''01™ W.), it will be for C'-l^, 75th 

 M. T. West, or 5''-6** G. M. T. Thus with these two observatories, the 

 resolution passed at Innsbruck in 1905, at the meeting of the Commission 

 on Terrestrial Magnetism and Atmospheric Electricity of the International 

 Meteorological Committee,^ will be followed in effect at 11 observatories, 



^Terr. Mag., vol. 10, 1905, p. 198. 



