170 ELEMENTS OF STATIC ELECTRICITY. 



above in a small, T- shaped piece of metal : to which 

 are attached, at the extremities of the cross piece, two 

 fibers of unspun silk ; by which the needle is suspended 



Fig. 55 Thomson's Quadrant Electrometer. 



from a projecting arm, supported, in the upper part of 

 the instrument, on a vertical glass rod. When the 

 needle is at rest, in the fixed position between the 

 quadrants, as shown in Fig. 56, the silk fibers hang 

 parallel to each other, and the cross piece, below, is 



