oSV *. 



242 Dr. 0. Lodge on the Electrostatic Force between 



of parallel wires which would jnst not let any radiation pass 

 through it. Suppose, for instance, that a grid with wires 

 10 centimetres apart satisfies this condition ; then each wire 

 mops up energy for a hreadth of 5 centimetres on either side 

 of itself. The heat generated in such a wire at each spark is 



3 _bl_ 1 

 2 " 47rr 2 ' 2 



This, in the numerical case already taken, with ^ = 1 *4 centim. 



and KV 2 =(88) 2 dynes, gives, at a distance of 1 metre, 



25x(100) 2 X 7 X ( 88 ) 2 = 32 * 5 er S s P er s P ark » 



which, repeated 100 times a second by a suitable contact- 

 breaker, would yield 3250 ergs per second, or 1 ordinary 

 thermal unit every 3J hours. 



The dissipation-factor, mentioned at the end of last section, 



!g Q 1-4X12X81. 



Attempt at further detail. 



To work out more completely what happens when one 



oscillator is used to excite another arranged parallel to it at 



an equatorial distance r, not near enough to re-act, I suppose 



we may consider the receiver as subjected to an impressed 



E.M.F. given by (8), and write down the equation to its 



current x at any instant, 



I'Y 

 x+2tcx + n /2 x = - 1 r-£e- mt $m (qr— pt), . . (12) 



the solution of which is given (for instance) in Lord Eayleigh's 

 ' Sound/ vol. i. p. 62. 



f- 



The heating of the receiver at each spark will be I Wx 2 dt. 



Jo 

 If there be two such receivers, far enough off each other not 

 to encroach on each other's field, the current attraction be- 

 tween them will be proportional to x l x 2) and the static 

 repulsion to x 1 x 2 . 



Calling the right-hand side of the above equation U, and 

 writing n /2 —/c 2 = n 2 , the complete solution is 



x= - f '«-«<'-*> sin nft-tO . TJ'M 



71 Jo 



#0 



cos 7 



. e~ Kt cos (nt-y); . . . (13) 



