206 PROCEEDINGS OF THE AMERICAN ACADEMY 



by curious thin detached sparks. An attempt was made to measure 

 the increase of light in Geissh-r tubes by Vierodt's photometric appa- 

 ratus, but it was found too inexact for this purpose, if, indeed, there 

 was any increase of light, which certainly remains to be proved. I 

 know of no results which bear upon the relation of the increase of 

 light to the increase of electro-motive force of the induction spark. 



Without condensers in the secondary circuit, however, the increased 

 electro-motive force of the spark was shown by its greater constancy 

 in leaping over a given resistance of air. 



The results of this investigation can be thus summed up : — 



1. The application of thin plates of iron as armatures to two strait 



electro-magnets increases between four and five times the strength 

 of the spark produced by the surrounding secondary coils. 



2. The length of the spark is doubled, which is only shown by the use 



of a condenser in the secondary circuit. 



3. The results show that it would be more economical to construct 



induction coils consisting of two strait electro-magnets constituting 

 the primary circuit, and two fine coils constituting the secondary 

 circuit, with the use of thin plates of iron as armatures to the 

 electro-magnets, than to distribute the same amount of wire ou 

 one strait electro-magnet, as in the common form of Ruhmkorf 

 coil. . 



NO. v. — ON THE SO-CALLED ETHERIC FORCE. 



Articles have appeared in various newspapers during the past few 

 weeks, calling the attention of the public to the evidences of a new 

 force discovered by Mr. Edison, of Newark, N.J., whicli he has 

 termed the Etheric Force. The New York " Triblme " of December 

 9th contains a letter from Dr. G. M. Beard, which details some experi- 

 ments which he has tried ; and in the same letter Dr. Beard invites 

 the attention of scientific men to the alleged new phenomena. 



Evidence of the force is obtained in the following manner : A bar 

 of cadmium or other metal — cadmium having the preference — is 

 placed upon the poles of a strong horse-shoe electro-magnet, in the 

 same manner that a soft iron armature is usually placed ; an insulated 

 wire is connected with the bar of cadmium ; and when the cii-cuit in 

 which the electro-magnet is placed is rapidly interrupted, either by a 

 key or a vibrating armature, sparks appear at the end of the wire con- 

 nected with the bar of cadmium. It is claimed that the kind of elec- 

 tricity thus evolved does not answer to the usual tests of static 



