with an Insulated Room. 173 



prime conductor with the rubber connected to surrounding ob- 

 jects^ consists simply of the resistance of the dielectric sepa- 

 rating the prime conductor from the surrounding objects, 

 and is therefore the same whether the room is connected to 

 earth or not. More complete views on this subject will be found 

 in what I have written before, both in my ' Electrical Accumu- 

 lation^ and in a paper " on Inductive Circuits, or the Application 

 of Ohm^s Law to Problems of Electrostatics,^^ in the Philoso- 

 phical Magazine for May 1868. 



Dr. Pergusou, in his ^Electricity,^ seems to have a tendency to 

 discard the older explanations; but at times his explanations ap' 

 pear to me incomplete, so that it is impossible to form an opinion 

 as to what his theory is as regards the actions that take place. 



The following paragraph, however, appears to me remarkable, 

 as it seems to show a tendency towards the theory which I have 

 advocated : — 



" We have hitherto taken no notice of the — E that, for in- 

 stance, is said to be lost in the ground when glass is charged 

 positively. Now it may be lost, and the — E induced by the 

 glass on surrounding conductors may be new — E induced by 

 it. But it is also possible, nayy even 'prohahle'^, that this — E is 

 none other than the — E said to he lost. If this be the case, the 

 ground acts as much on the glass as the glass on the ground ; 

 and the action is i^recisehj the same as in a galvanic circuity when 

 the polarization proceeds in opposite ways in two opposite direc- 

 rections, the action of the one strengthening the action of the 

 other.'' 



Here we have stated as probable what I have urged ten yeai's 

 ago, and which I think I have now demonstrated by experiment. 



Dr. Perguson adds, " However, it makes no practical differ- 

 ence ; and it is simpler to suppose the insulated body to be the 

 one centre of force."" With this last paragraph I cannot agree, 

 as it will be found that, by considering problems of electrostatics 

 by means of the theory of inductive circuits, many can be solved 

 which cannot be explained by an allusion to the earth as a com- 

 mon reservoir. The experiment with the insulated room is only 

 one of them, I maintain that no electricity is ever lost in the 

 ground or drawn from the ground as a reservoir. All electricity 

 generated, if we consider it as a quantity, is produced in equal 

 quantities, and can only be neutralized by an equal quantity of 

 electricity of the opposite name. 



Thus when the sphere in the insulated-room experiment was 



charged positively from the prime conductor, an equal quantity 



of negative v/ent to the room. When the sphere was taken out 



of the room, this negative w^ent to the outside of the room at 



* The itahcs are mine.— P. C. W. 



