Defaiptlon of a Simple and Poiverful EleBrical Machine. g^ 



zontal, tlic cylindrical ends may be placed in contaft with the cuftions, and the prime con- 

 duaor inftantly exhibits negative eleftricity. But as it is neceJary that the cufhions fliould 

 communicate with the ground when the pofitive power is wantedj and that they fliould be 

 infulated when the negative power is required, there is another femicircular branch applied 

 to the oppofite fide of the plate nearly at right angles to the iirfl:. That is to fay, when 

 pofitive eledricity is wanted, this fecond branch denoted by I. I in the feftlon Fig. i, PI. IV, 

 is placed nearly horizontal, and forms a communication from the culhions to the ground 

 through a metallic rod from K behind the mahogany pillar which fupports the a.vis ; but 

 when on the contrary the negative power is wanted, and the branch from the prime con- 

 dudor is placed in contaft with the cufhions, this other branch from the axis is put into the 

 vertical fituation, and carries off the ekariclty emitted from the plate ofglafs. 



The axis of the plate Bh, Fig. i, Plate IV, is fupported by a fingle column A, which for 

 that purpofe is provided with a bearing-piece K, on which two brafs collar-pieces DD re- 

 prelented more at large and in face in Fig. 3, are fixed, and carry the axis itfelf. The 

 whole of Fig. I, is reduced to one-eighth of its real dimenfions, unlefs contrailed by the 

 fhrinkmg of the paper after printing ; to obviate which, it may be remarked that the dia- 

 meter of the plate is 31 Englilh inches. The axis has a counterpoife O, of lead, to prevent 

 too great fridion in the collar D neareft the handle. The arc of the condudorEE, which 

 carries the two fmall receiving conduftnrs FF, is fixed to the axis G, which tun'-5 in the 

 ball H. On the other fide of the plate is feen the other arc II, of brafs wire, half an inch m 

 diameter, fixed to the extremity of the bearing-piece K, fo that it may be turned in the Eime 

 manner as the arc EE. The two receiving conduaors FF are fix inches long, and two and 

 a half inches in diameter. The double line P reprefents a copper tube terminating in a ball 

 Qi, It moves like a radius upon the ftem R of the ball S, which being fcrewed into the 

 conduaor H, feives to confine the arm P in any pofition which may be required. The dia- 

 meter of the ball S is only two inches, which, together with certain other lefs rounded parts 

 of this apparatus, may ferve to fl.ew that the confiderable ekaricity from this machine 

 IS lefs difpolcd to efcape than if it had proceeded from a cylinder. The dilfipation of elec- 

 tricity along the glafs fupports is prevented by a kind of cap T, of mahogany, which affords 

 an elcarical well or cavity underneath, and likewife effeaually covers the metallic caps in- 

 to which the glafs is cemented. The lower extremity of the cap is guarded in the fame 

 manner by a hollow piece or ring V, of mahogany, which covers the metallic fockct into 

 which the glafs is cemented. The three glafs pillars arc fet in Hiding-pieces, as marked on 

 theplatfovm of Plate III, which are 9 inches long. 



The rubbers of this machine differ in no effencial particular from thofe dcfcribed by the 

 inventor in the Journal de Phyfique for February 1791 ; and the apparatus for applying 

 them is defcribed in the fame work for April 1 789. Fig. 2. reprefents a fedion of this ju- 

 dicious piece of mechanifin feen from above, and one-fourth of the real fize. A metallic ■ 

 fliding-piccc bb, is Aided into a correfpondent face, on the ball Z, which is one of thofe fixed 

 on the top of the glafs pillars near the circumference of the glafs plate in Plate III. To 

 this is affixed the piece dd, which terminates in two hinges gg, that allow the fpringscc to 

 move in tlie plane of the horizon. The pieces gg reprefent the wood-work of tlic cufhions 

 attached to the extremities of the fprings by the hinges hh. The fprlngs are regulated by 

 the bolt and fcrcw ii. The two cufliions arc thus made to apply to the plate equally through 



their: 



