384 Mr. W. B. Morton on the Effect of Capacity 



so that no standing oscillations were formed in the wires. He 

 found that when a condenser was inserted it caused reflexion 

 of the waves, and a series of nodes and loops could be found 

 in front of the condenser. Mazzotto * in a recent research 

 has availed himself of the effect of an isolated capacity to 

 produce a gradual change in the wave-length of the oscilla- 

 tions. He uses pieces of wire hung on to the parallel wires. 



The theory of electric waves in wires has recently been 

 treated in an exhaustive manner by Drude f. His method 

 consists in following out in detail the various reflexions 

 undergone at the bridges by a wave-train which starts from 

 the end of the wires. The state of affairs at a point of the 

 circuit is obtained by summation of a series of separate dis- 

 turbances due to the different direct and reflected trains. 

 The calculations are rather complicated. In obtaining a 

 formula with which to compare my observations I have used 

 a method adapted from some work of Mr. Heaviside's % . Apart 

 from the actual results obtained, the investigation is perhaps 

 of some interest as showing how easily some problems con- 

 nected with oscillations in wires can be attacked by this 

 method. 



The experiments were made, for the most part, at the end 

 of the parallel secondary wires remote from the oscillator, 

 the arrangement being as shown in the diagram. 



C is the end condenser of capacity S 2 . S x an interposed 

 condenser. The vacuum tube was placed across the plates of 

 S 2 . The plates of S, and S 2 were kept at a constant distance 

 apart while the position of S x was varied. A nodal position 

 B of the bridge having been found so that the tube shone, 

 B was left on the wires, and A laid on and adjusted so that 

 the tube remained bright. Then A, B are nodes of the same 

 system. Owing to the finite length of the bridge the 

 potential-difference at its ends is not quite zero, the true 

 node falling at the centre of the bridge. Accordingly, if the 

 bridge B is taken off the wires the nodes will fall a short dis- 

 tance to the left of B— roughly half the length of the bridge. 

 This distance Drude has called the " bridge-shortening." In 



* Nuov. Cim. [4] ii. pp. 296-311 (1895) ; Wied. Beibl xx. p. 392. 

 t Abhandl der Sachs. Ges. dei* Wiss. xxiii. pp. 64-168 (1896) ; Wied. 

 Ann. lx. pp. 1-46 (1897). 

 % ' Electrical Papers,' ii. p. 194 et seq. 



