274 CARNEGIE INSTITUTION OF WASHINGTON. 



Pole have been sent to Groningen, where they are now being measured. 

 Both the positions and the diameters are being measured in dupHcate. 

 Near the Milky ^\'ay the fields are 15' by 15', in higher latitudes 20' 

 by 20'. A precision of about 1" in each of the coordinates is aimed at. 

 Of course the most important part of the work is the determination of 

 the magnitudes, which is made possible with the aid of standards now 

 being determined by Mr. Seares. Of the 139 areas, 107 have been 

 completely measured. The total number of stars thus far is some- 

 what less than 40,000. 



The fields are so small that our meridian catalogues do not furnish 

 the necessary standards for position. These are therefore taken from 

 the more comprehensive survey of the Selected Areas made with the 

 aid of Harvard and Arequipa plates. These plates go down to about 

 the sixteenth magnitude. The Mount Wilson plates will extend the 

 range to about eighteenth magnitude. 



PROFESSOR STORMER'S INVESTIGATIONS. 



Professor Carl Stormer, of the University of Christiania, Research 

 Associate of the Carnegie Institution of Washington, has completed 

 his preliminary work on solar vortices for publication in the Con- 

 iributions. The most striking result obtained is the extremely large 

 electric field which would result if we consider the Zeeman effect in 

 sun-spots due to a convection current of electricity. This seems 

 quite irreconcilable with the apparent absence of the Stark effect, and 

 the possibility that galvanic currents may play an important part in 

 sun-spots must be given serious consideration. 



These different working hypotheses will be further developed and 

 settled when more material regarding the electromagnetic fields 

 around sun-spots is obtained. 



In the same paper are also developed some important consequences 

 of the equations of motion of an electric particle in the electromagnetic 

 field at high levels over the spot. 



PHYSICAL LABORATORY. 

 INSTRUMENTS. 



An important addition to the equipment of the laboratory is 

 a complete outfit for the study of the Stark effect. This includes 

 a Stark tube, filled with hydrogen, for which we are indebted to the 

 kindness of Professor Stark, who had it made in his laboratory and 

 tested it for us. The generating plant, installed in a small house 

 erected behind the office building, consists of 40 one-half horsepower 

 550- volt D. C. General Electric motors (used as generators), mounted 

 in 5 groups of 8 each, and driven by a 15-kw. 3-phase synchronous 

 motor, run at 1,800 R. P. M. The lead wires are brought into 

 a laboratory room in the basement of the office building, where the 

 switches, voltmeter, tubes, spectrograph, and other instruments are 



