234 Intelligence and Miscellaneous Articles. 



W. Weber's theory assumes. Those experiments might possibly 

 have been decisive against the existence of such an action. They 

 were not so; but, on the other hand, through this negative result 

 the existence of the action in question remained unproved. Mr. 

 Rowland has now carried out a series of direct experiments, in the 

 physical laboratory of the University here, which give positive proof 

 that the motion of electrified ponderable substances is also electro- 

 mngnetically operative. I here remark that he had already con- 

 ceived and fully considered the plan of his experiments when he 

 came to Berlin, without any previous cooperation on my part. 



The moved bearer of the electricity was a disk of ebonite 21*1 

 centims. in diameter and J centim. thick. It could revolve with 

 great velocity (up to 61 times in a second) about a vertical axis 

 fixed in its centre. The ebonite disk was gilt on both sides ; but 

 the gilding was insulated from the axis. Near it, above and below, 

 were placed glass disks of 38-9 centims. diameter, pierced through 

 the middle to admit the axis of the ebonite disk. The glass disks 

 were likewise gilt, in an annular band of 24 centims. external, 8*9 

 internal diameter ; the gilt side was mostly turned toward the ebo- 

 nite disk. The gilt surfaces of the glass disks were, as a rule, con- 

 nected to earth ; while the ebonite between them, through a point 

 directed toward it at a distance of g millim. from its margin, was 

 in electrical communication with the coatings of a large insulated 

 Leyden battery which served as a reservoir for the electricity. A 

 commutator of a peculiar construction, inserted between them, per- 

 mitted now the one, now the other coating to be connected either 

 with the ebonite disk or with the earth. In the construction of 

 these parts, iron was avoided. 



Close above the upper glass disk an extremely sensitive astatic 

 needle was suspended to an arm fixed in the wall, and completely 

 enclosed in a brass case connected to earth. The two needles were 

 1*5 centim. long, but at a considerable distance (17*98 centims.) 

 from each other. Their deflections were read off with a mirror and 

 a telescope. The opening in front of the mirror was protected from 

 external electrical influences by a metallic hollow cone. Indeed 

 the electrical charge of the battery and the reversal of the electrifi- 

 cation of the ebonite disk gave no perceptible trace of action on the 

 needle so long as the ebonite was stationary. 



On the other hand, on swift rotation, even without electrifying, 

 the action of rotation-magnetism was shown, mostly arising from 

 the brass axis of the rotating disk, and considerably diminished by 

 reducing it to 09 centim. thickness. The action of the electrifica- 

 tion of the disk could be separated from that of the rotation-mag- 

 netism by letting-in alternately positive and negative electricity 

 (by means of the commutator above-mentioned) while the velocity 

 of the rotation was maintained unaltered. The displacement of the 

 needle from the position of equilibrium amounted to from 5 to 7y, 

 its arc of oscillation on changing the electrification, therefore, to 

 from 10 to 15 scale -divisions. This result ensued in hundreds of 

 observations (which were made with gradually and continually 

 more and more improved apparatus in the course of several weeks), 

 and always in the same direction. The direction of the deflection 



