[ 165 ] 
V. The Mechanical Forces Acting on a Charcjed Electric Condenser inoring 
through Space. 
By Professor F. T. Teoutox, F.P.S., and H. Ii. Noble, B.Sc., University College, 
London. 
iJec-eived June 11,—Bead June 18, 1903. 
The experiments described in this paper were designed witli tlie oliject of 
investigating the beliavioni- of a charged electrical condenser moving through 
space, and to discovei’, if possible, Avhether there he a relative motion between the 
earth and the aether. It was previously suggested by one of us in tlie ‘ Proceedings 
of the Pvoyal Dublin 8oc.’ (Vol. VII., Part XIV., April, 1002), in connection with 
an experiment of a similar nature suggested by the late Professor FitzGeh.\,ld, and 
mentioned in his collected pa})ers edited by Professor Larmob. 
The idea underlying the experiments will be understood from the following 
considerations ;—If a charged condenser be jdaced with its })lane in tlie direction of 
the aether drift, then, on the assumption that a moving charge develo]js a magnetic 
field, there will be associated with the condenser a magnetic field perpendicidar to 
the lines of electric induction and to the direction of the motion. Wlien the plane 
of the condenser is per})endicular to the fetliei’ drift, the effects of the opposite 
charges will neutralise each otlier. Thus there is magnetic energy stored in the 
medium when the plane of the condenser and the direction of the drift coincide ; 
and accordingly it is to be expected that undei- these circumstances the condenser, 
when freely suspended, would tend to move so as to take up the position with its 
plane perpendicular to the drift, in order to transform this energy.'''" 
To realise this, a condenser, with its plane vertical, was suspended l»y a fine wire 
and charged. The charges were let into tlie plates of the condenser by means of the 
suspending wire, and by a wire which hung from beneath, dipping into a liquid 
terminal. Observations were made at different times in the day, when the plane of 
tlie condenser made various ano-les with the direction of the drift. If the condenser 
* [According to the theory given Ly L-VPAIOR (‘FiTZGERAi.n’s Scientific Papers,’ p. 566) the longi- 
tirdinal direction, l)eing that of maximum kinetic energy, i.s the direction of equililirium; the force.? due to 
displacement from it hoirever remain as above, if the form of the system be assumed permaneiit. The 
negative electric exjjerimental result reached in this paper is connected with the other negative second- 
order re.sults of optical experiments relating to motion through the lether, which have been obtained 
by Michelson and by Eayi.eigu. The inferences as regards molecular theuiy are indicated lor . cit .'] 
VOL. CHII.- A 350. 
31.10.03 
