306 CARNEGIE INSTITUTION OF WASHINGTON. 



Other experiments were made with single plates in fieMs intense over a 

 central zone and rapidly diminishing in strength toward the ends. In some 

 the intensity at the center was normal to the plate, in others, parallel. In 

 no case was any variation found in the intensity of the photographic effect. 

 In other experiments only a segment of the copper top, instead of the whole 

 top, was coated with rosin, and only a portion of the plate, partially under- 

 neath one end of the rosin, was placed in an intense magnetic field. No effect 

 of the field was manifest. 



As would be expected from the nature of these effects, according to the 

 theory of Russell, direct experiments made to see whether a beam of the 

 radiation involved could be produced and be deflected by a magnetic field 

 were complete failures. 



A report on electromagnetic induction. S. J. Barnett. 



This report discusses briefly the chief fundamental results obtained from 

 the days of Faraday to the present time in studying the electromotive forces 

 ordinarily referred to the domain of electromagnetic induction. 



Self-induction is first taken up and the phenomena of self-induction are 

 treated as essentially identical with the phenomena of inertia in dynamics, 

 according to the idea of Maxwell and the idea originally accepted by Fara- 

 day. The only recent fundamental progress has been in studying the inertia of 

 free electrons and other ions, and experiments are referred to on this subject. 



The motional electromotive force, developed when matter moves in a mag- 

 netic field, is next considered, and is derived from Ampere's law on the electron 

 theory. Especial attention is devoted to the motional intensity, and the 

 resulting electric displacement, in insulators, of which nothing has been known 

 until recent years. 



The induced electromotive force in fixed conductors and insulators arising 

 from the motion or alteration of other systems is next considered, and is 

 expressed both in terms of magnetic flux and in terms of the general vector- 

 potential, which refers the phenomena back to the motion of electrons without 

 the magnetic field as intermediary. The relations between the induced and 

 motional electromotive forces are discussed, as well as the relation of the 

 electric displacement produced in certain cases to the hypothesis of the fixed 

 ether. 



The report closes with a treatment of unipolar induction in both so-called 

 open and closed circuits, including brief descriptions of some of the principal 

 experiments, a discussion of the theories involved, and their application to the 

 unipolar generator. 



Results of magnetic and electric observations made during the solar eclipse of June 8, 

 1918— Concluded. L. A. Bauer, H. W. Fi.sk, and S. J. Mauchly. Terr. Mag., 

 vol. 24, 1-28, 87-98 (March and June 1919). Washington. 



Part 1, being the conclusion of the investigations concerned with the mag- 

 netic observations made during the solar eclipse of June 8, 1918, by the 

 Department of Terrestrial Magnetism and cooperating magnetic observatories 

 and universities, summarizes the chief conclusions derived from the magnetic 

 observations as follows: 



(a) Appreciable magnetic effects were observed during the solar eclipse 

 of June 8, 1918, at stations distributed over the entire zone of visibility and 

 immediately outside. (How much further some of the effects may have 

 extended must be left for future study.) The chief characteristic of the effects 

 took place generally in accordance with the local eclipse circumstances and 

 in general accord with effects observed during previous eclipses. The evi- 

 dences of a direct relation between the magnetic effects and the solar eclipse 



