Hare's Electrical Plate Machine. 109 



My plate {thirty-four inches in diameter) is supported 

 upon an upright iron bar, about an inch in diameter, cover- 

 ed by a very stout glass cylinder, four inches and a half in 

 (diameter, and sixteen inches in height, open only at the 

 base, through which the bar is introduced, so as to form its 

 axis. The summit of the bar is furnished with a block of 

 wood, turned to fit the cavity formed at the apex of the cy- 

 linder, and cemented therein. The external apex of the 

 cylinder is cemented into a brass cap, which carries the 

 plate. The glass cylinder is liable to no strain ; it is only 

 pressed where it is interposed between the block of wood 

 within, and the brass cap without. The remaining portion 

 of the cylinder bears only its own weight, while it effectu- 

 ally insulates the plate from the iron axis. The brass cap 

 is surmounted by a screw and flange ; by means of which, a 

 corresponding nut, and disks of cork, the plate is fastened. 

 A square table serves as a basis for the whole. The iron 

 axis, passing through the cover of the table, is furnished 

 with a wooden wheel of about twenty inches diameter, and 

 terminates below this wheel in a brass step, supported on a 

 cross of wood, which ties the legs of the table diagonally 

 together. The wheel is grooved, and made to revolve by a 

 band, which proceeds from around a vertical wheel, outside 

 of the table. This external wheel has two handles; it 

 may of course be turned by means either of one or both. It 

 is supported on two strips of wood, which, by means of 

 screws, may be protruded, lengthwise, from cases^ which 

 confine them from moving in any other direction. By 

 these means, the distance between the wheels may be va- 

 ried at pleasure, and the tension of the band duly ad- 

 justed. 



Nearly the same mode of insulation and support which is 

 used for the plate, is used in the case of the conductors. 

 These consist severally of arched tubes of brass, of about 

 an inch and a quarter in diameter, which pass over the 

 plate from one side of it to the other, so as to be at right 

 angles to, and at a due distance from each other. They 

 are terminated by brass balls and caps, which last are ce- 

 mented on glass cylinders, of the same dimensions, nearly, 

 as that which supports the plate. The glass cylinders are 

 suspended upon wooden axes, surmounted by plugs of cork, 

 turned accurately to fit the space which they occupy. The 

 cyHflderg ar« kept steady, below, by bosses of wood, which 



