262 On Galvanic Agency^ 



extended a column to 10,000 groups of small diameter, and 

 placed them in glass tubes, 



Mr. G. S. Singer has subsequently improved it materially by 

 interposing two disks of paper instead of one, which increased its 

 power considerably, and thus lessens the labour of construction. 

 He extended his series to 20,000 groups, and has filled up an 

 apparatus of two small columns in a very convenient form for 

 ringing a pair of bells. But I have constantly preferred the ser 

 coiid method employed by M. De Luc for observing the phae.- 

 nomena of this curious instrument, Avhich I have oideavoured to 

 render more convenient by using a much larger ball on the pen- 

 dulum; by making this pendulum of an inflexible wire instead 

 of the fine silver thread ; by causing it to partake of the motion 

 of the conniion pendulum with that of electric attraction, and 

 by applying its vibrations to the motion of indexes. It would 

 not be just to omit here my acknowledgement of obligation to 

 Mr. Gorham, a very ingenious watch-maker at Kensington, 

 from whom I received great assistance, and who executed the 

 mechanism of the wheels, levers, &c. in a very neat and accurate 

 manner. 



AA, &c. (Plate V.) are six of Mr. Singer's columns in glass 

 tubes, supported by two stems of glass covered with sealing- 

 vax BB, and the flat pieces of brass CC, &c., which pieces 

 serve also to render them co};tmuous : the positive extremity P 

 is connected by a brass wire with the dial plate D ; and the 

 negative extremity N, with the screw 6. The dial plate is sup- 

 ported by a stem of glass projecting from the piece of wood E 

 behind it. The pendulum, Avhich is a wire of steel of about 

 l-50th of an inch diameter and 14 inches long, carries a ball 

 of gilt coik about one inch diameter : this when nnelectrified 

 hangs at about 4-lOths of an inch from the disk. No. 1 and 2 

 is a bow stretching a fine silver wire, and is attached to a spring 

 so that it can be advanced towards or withdrawn from the peudu- 

 lum by turning the screw 3. 4 is a flat piece of brass carrying 

 the support of the disk &c. 5, and has a groove which allows 

 the lower part of the screw 6 to pass through, so that the disk 

 and bow may be placed and hrndy secured at the required di- 

 stance from the bob of the pendulum, which is ascertained by 

 a great many trials. The whole is covered with a large glass 

 shade. Fig. 2 is a front view of the mechanism attached to the 

 dial plate, of the exact size of the original. No. 1 is the top of 

 the pei)d'',luni, which is suspended from the peg 2 by a piece of 

 fine watch pendulum wire. I have not drawn tlie lower part, be-' 

 cause it would obstruct the view of the crutch 3. This crutch 

 gloves on die pivot 4, and carries at the upper end a sniall lever 5, 

 '' ' ■ ' which 



