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V. On the Direct Conversion of Dynamic Force into Electricity, 

 By S. Tolver Preston, Esq.* 



IT is a well-known fact that electricity is capable of direct 

 conversion into motion, this principle being illustrated in 

 its simplest form by the use of apparatus in which metallic cir- 

 cuits alone are employed, motion being effected, as in the case 

 of the apparatus of Ampere, without the use of either commuta- 

 tor or magnet. As far as I am aware, the exact converse of 

 this case, i. e. the direct conversion of dynamic force into elec- 

 tricity without the aid of magnetism, has not been shown to be 

 possible. The apparatus of Faraday, consisting of a metallic 

 disk caused to rotate between the poles of a permanent magnet, 

 is well known — the current thus induced in the disk having 

 been conducted through a galvanometer whose terminals were in 

 connexion with the axis and circumference of disk respectively. 



In the annexed figure the helix S takes the place of the gal- 

 vanometer, one extremity being in con- 

 nexion with the circumference of disk D 

 through a spring S', the other extremity 

 being connected in any convenient man- 

 ner with the axis. 



In the apparatus of Faraday the cur- 

 rent induced in the disk was solely due 

 to the influence of the permanent magnet, £ ~~ 

 the current traversing that portion of the circuit formed of the 

 galvanometer producing no useful effect. Supposing, however, in 

 the present case the pole of a magnet or a second separate helix 

 traversed by a current (from any source) to be placed near and 

 parallel to the helix S, then the current thus induced by the 

 rotation of the disk will traverse the helix S which forms part of 

 the circuit of the apparatus, and (by a suitable direction of rota- 

 tion) the direction of the current in both helices will be identical. 



The current traversing the exterior circuit is therefore by this 

 arrangement capable of contributing to the effects, both helices 

 being similarly situated in relation to the disk and traversed by 

 a current in the same direction. 



Moreover, the helix S forming part of the circuit of the appa- 

 ratus, the intensity of the current traversing it is therefore a 

 function of the velocity of rotation. 



The inductive influence on the disk of the helix S, which de- 

 pends on the intensity of the current traversing its coils, is 

 therefore capable of indefinitely exceeding that due to the sepa- 

 rate helix, in which the intensity of the current, whatever the 



* Communicated by the Author. 



