394 Intelligence and Miscellaneous Articles. 



ring of the figure described above. In their middle are very delicate 

 stars, for the most part with four or five rays. 



Hence we have here both the positive and the negative Lichten- 

 berg's figures, and upon those plates, too, upon which, from the laws 

 of induction, they ought to be. 



The diameters of these figures are independent of the thickness of 

 the plates, of the size of the coatings, and even of the intensity of the 

 inducing battery, provided this does not exceed certain limits, but 

 vary with the distance of the plates. 



The influence of this element is shown in the following Table, 

 which contains the mean value of several observations : — 



Distance of the External diameter Internal diameter 



plates. of the ring. of the ring. 



d 2-1 4-0 



2tf 3-8 7*7 



2d 5*5 110 



Ad .... 9-3 14-5 



An increase in the strength of the inducing battery is accompanied 

 by an increase, but not by a change in the shape, of the figures. 

 Only when they exceed a certain limit do the figures become indi- 

 stinct through overlapping. 



If the interruption of the current be repeated, and if in the interval 

 an observation be made, it can be seen how, first, the number of 

 figures increases, as by each break new ones are formed, and how, 

 finally, by overlapping they pass into those first described. 



If instead of the glass plates ebonite plates are used, the same 

 figures appear, though somewhat larger. Also if the plate coated on 

 one side be replaced by one coated on both sides, or by a metal 

 plate, figures are formed on each, the more minute description of 

 which must be reserved for another opportunity. — Sitzungsbericht 

 der konigl. lair. Akad, der Wissenschaften, July 1869. 



ACTION OF SODIUM ON ACETIC ETHER. 



An important step in this controversy has been taken by M. La- 

 denburg, who has recently sent a note to the Chemical Society of 

 Berlin, in which he confirms Mr. Wanklyn's observation that pure 

 acetic ether evolves no hydrogen when sodium acts upon it. M. 

 Ladenburg renders acetic ether free from the last traces of alcohol 

 by bringing it into contact with a little chloride of silicon, which 

 attacks alcohol, but is without action on acetic ether. 



ON THE PERIODS OF CERTAIN METEORIC RINGS. 

 BY DANIEL KIRKWOOD*. 



I. The Meteors of April 20th. 



In the Astronomische Nachrichten, No. 1632, Dr. Weiss called 

 attention to the fact that the orbit of the first comet of 1861 very 

 nearly intersects that of the earth in longitude 210°, the point passed 

 by the latter at the epoch of the April meteoric shower. A. relation 



* Communicated by the Author from the Proceedings of the American 

 Philosophical Society. Read March 4, 1870. 



