Intelligence and Miscellaneous Articles. 41 1 



millims. ; with a single middle-sized Leyden jar it was about 30 

 millims. ; with eight like jars arranged in series the discharge at- 

 tained. 130 millims. We then used jars of almost double size ; with 

 a single one the striking distance was about 1 7 millims., eight gave a 

 spark of 82 millims. The addition of a ninth increased the spark by 

 8 millims. In this mode of working, the successive condensers dis- 

 charged themselves immediately after having been charged. To 

 retain the charge, one of the poles of the coil must be joined to the 

 final external armature, and the induction spark taken between the 

 other pole and the first internal armature. The series becomes charged 

 very rapidly, and it can be discharged with the ordinary discharger ; 

 the elongation of the striking distance is observed as in the first 

 case. 



The same phenomena are reproduced with the ordinary electrical 

 machiue ; I have repeated the experiment in the laboratory of the 

 Lycee at Versailles, and the general result agrees with the prece- 

 ding. 



M. Ruhmkorff and myself think that this new mode of discharging 

 condensers may be useful in a great number of cases. With a cer- 

 tain number of Leyden jars, associated either in battery or in series, 

 discharges will be obtained, suited by the tension and by the quantity 

 of electricity expended, fjr the most varied effect. M. Huhmkorfr* 

 has already witnessed the application cf this method to the beautiful, 

 researches of MM. Pliicker and Hittorf. The satisfactory result which 

 we obtained by passing the discharge in a capillary tube arranged 

 like theirs, but containing gas at the ordinary pressure, leads us to 

 hope that the arrangement in series might be useful to them.— 

 Comptes Rendus, February 16, 1863. 



ON SOME REMARKABLE NUMERICAL APPROXIMATIONS. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 

 The very close approximation which Metius obtained by using 

 the fraction — as the proportion existing between the diameter and 



the circumference of a circle, induced me to seek for other fractions 

 which should approximately represent the decimal values of various 

 other problems. 



The result of my investigations I have embodied in a Table, which 

 M. Babinet has done me the honour to lay before the Academie des 

 Sciences at their meeting on the 6th instant. I beg to annex a copy. 

 My intention is to extend the Table as soon as I can find sufficient 

 leisure. 



I remain, Gentlemen, 



Your most obedient Servant, 



April 20, 1863. Charles M. Willich. 



f :i- 



