ON THE ELECTRIC COLUMN. iQ^ 



with the two extremities of this long column* Mr. Forster 

 has described this new kind of chime in a letter to Mr. Til- 

 loch, published in the Phil. Mcgaz. of the latter, mention- 

 ing this singular circumstance, that the ringing began on 

 the jubilee day. Since that time I have had the pleasure of 

 being personally acquainted with Mr. Forster, and he has 

 lately informed me, that, having mounted again this chime 

 on the 25th of March, it has not ceased to ring ever since. 

 This is a curious application of the property of the column, 

 but, as I have explained, it cannot answer the purpose of 

 regular observations. 



For the execution of the above mentioned plan, I first Addition to the 

 made the following addition to my apparatus. At the top apparatus. 

 of one of the pillars of the column, on its side A (the posi- 

 tive extremity, I fixed a brass piece 13, held there by a 

 ferrule, and projecting forwards about l~ inch : on this pro- 

 jection is fixed, by a screw, another brass piece, having on 

 one side a vertical groove 14, in which is held, by a pin, a 

 brass rod, at the lower part of which is a large brass ball 15, 

 which can be moved backwards and forwards, in order to 

 bring it to the convenient point, where it remains steady, 

 by the friction of the top of the rod in the groove. From 

 this top projects a brass loop l6, to which is suspended a 

 gold bead I7, by the thinnest silver wire, such as is used 

 for cross wires in telescopes ; and by moving properly the 

 ball 15, the bead is made to hang close to it, without lean- 

 ing against it: this is done while both the bead and the 

 ball are neutral, by handling the latter for this adjust- 

 ment. 



My purpose having only been at first, that the ball 1 8 

 should- be in communication with the ground, I produced 

 this communication in a simpler manner than is represented 

 in the ^f^ure; having changed it since for a purpose that I 

 shall explain ; but the difference is here of no consequence: 

 it was then only held at the top of a brass stem, fixed to 

 the end of a thick slip of lead 19, 19; movable backward 

 and forward between pins 20, 20, 20, in order that the 

 distance of this ball from the ball 15 might be changed, as 

 should be found proper for the strikings of the bead. 



This apparatus was finished iu the beginning of last 

 M 2 spriog : 



