«r First Mover for mechanical Purposes, 361 



peiiiliilum, being in conducting communication with the positive 

 extremity of the column, will necessarily recede from it and ap- 

 proach the opposite hall ; but it is prevented from actual con- 

 tact with that ball by a brass fork F, across wliicli a very fine 

 silver wire is stretched. This wire discharges the electricity of 

 the pendulum, and at the same time produces a kind of jerk 

 which prevents the pith-ball from sticking : the pendulum now 

 falls again into contact with the positive ball, but becoming 

 again electrical recedes from it and again strikes the cross wire; 

 and in this way, if properly constructed, may continue its vibra- 

 tions for an uulimiced period. 



I have sometimes made a variation in this apparatus, bv re- 

 moving the cross wire and the conducting support of the pendu- 

 lum, and by substituting for it a pith-ball suspended by a silk 

 thread, and accurately proportioned in weight and size to the 

 medium power of the column. By this means the motion occurs 

 over more space than in either of the preceding arrangements, 

 and is therefore more obvious, and well calculated for observa- 

 tion, as tiie irregularity is considerable, and ni^y be noticed when 

 the temperature of the surrounding me4ium varies but slightly. 



During my employment of the very extensive series of co- 

 lumns I have constructed, I have frequently attempted to produce 

 a rotatory motion by the direct action of their electrical power, 

 but hitherto the attempt has continued unsuccessful ; by indirect 

 meaiis, however, the same oiiject has of late l;cen very ingeniously 

 obtained. In Octvober last, my friend Mr. Lightfoot, a very ac- 

 tive philosopher, uiio has made many interesting observations 

 on this subject, first suggested the employment of an iiiflexible 

 pendulum as a means of converting tlie reciijrocat.ing motion 

 usually produced by the column into a source of rotatory move- 

 ment ; and the correctness of this idea was soon afterwards 

 practically verified by my pupil Mr. F. Ronalds, who with tl>e 

 assistance of a vv'atchniaker lias made a very successful and truly 

 ingenious arrangement, by which a simple and curious electrical 

 clock is produced. 



The rotatory motion obtained by this indirect means, is how- 

 ever rather curious tlian useful ; for it is scarcely so correct an 

 indication of the power of the column as the simple pendulum, 

 and requires a much more extensive series to keep it in motion; 

 it cannot therefore be preferred for the usual pur|)oses of obser- 

 vation, and has I fear very little chance of becoming at all use- 

 ful as a time-keeper; for the variable action of the cohunn must 

 render it a most irregular maintaining power, which it will be 

 very difficult, if not impossible, to correct effectually. 



The most elegant and at the same time the most simjile move- 

 iuent yet produced l>y the action of the electric column appeais 



to 



