c60 The Eleclrk Culumn coiisidered as a maintaining Powers 



sides of the glass, during their contact with one extremity of the 

 column, for a certain number oT seconds, becomes a measure of 

 the comparative power of the instrument at diifercnt times : but 

 its distinct expression is prevented by the tendency of tiie gold-, 

 leaves to stick to the sides of tlie glass ; and tliis arrangement is 

 therefore by no means fitted for permanent obspr\'ations. 



When an insulated conducting substance is freely suspended 

 between two balls, or bells, connected respectively with the op- 

 posite ends of the column, I have found that motion is con- 

 stantly produced, if the weight of the pendulum, and the distance 

 of the bells, are exactly proportioned to the acting jjower of the 

 column at its mean rate of intensity: but if these circumstances 

 are not strictly attended to, the motion will soon cease ; and the 

 want of complete success in the original experiments of M. De 

 Luc - and of Mr. B. M. Forster most probably arose from this 

 cause ; for, in the construction of a number of instruments ou 

 this plan, I have had but one failure, and in that instance tlie 

 apparatus was finished in such haste as to preclude a proper 

 attention to the circumstances above stated. 



Fig. 1. Plate VII, represents the arrangement of my Electric 

 Chime. A series of about 1600 groups of zinc, silver, and paper 

 disks, are disposed in two columns, separately insulated in a ver- 

 tical position ; the positive cvA of one column is placed lowest, 

 and the negative end of the other, their upper extremities being 

 connected so as to form in efiect one series, having at each of 

 \\.i extremities a small bell ; between the bells a small ball is 

 suspended by a thread of raw silk, so as to hang at an equal and 

 very small distance from each of them if unelectrifiedv. The 

 r.ttion of the column occasions this ball to vibrate between the 

 bells and produce an electric chime, in which the variable action 

 of the instrument at di.'Terent times is indicated by an increased 

 or diminished velocity of ringing. There is a circular groove in 

 the base of the instrument which receives the rim of a glass 

 shade, by which dust and moisture are prevented from impeding 

 its action. 



Fig. 2 represents a convenient modification of the arrange- 

 ment devised by M. De Luc, and to which he has given the 

 name of Aa-'ial Electroscope. It is constructed nearly in the 

 same manner as the chime, but has balls at its lower extremity 

 instead of bells. From the positive end a wire W proceeds up- 

 wards a few inches parallel to the column, and is tlirn bent into 

 a hook to serve as a support to the pendulum, which consists of 

 a fine silver wire to which a gilt pith-ball is attached. This 



' TJiib Plate will be given \vjt!i ilic next niinibtr. 



pendulum. 



