ELEMENTARY LESSONS ON [CHAP. i. 



serve equally well. When an electrified body is held near 

 the electroscope it is attracted and turned round, and will 

 thus indicate the presence of quantities of electricity far 

 too small to attract bits of paper from a table. 



13. Gold-Leaf Electroscope. A still more sensi- 

 tive instrument is the Gold-Leaf Electroscope in- 

 vented by Bennet, and shown in Fig. 7. We have 

 seen how two pith -balls when similarly electrified repel 

 one another and stand apart, the force of gravity being 

 partly overcome by the force of the electric repulsion. 



Fig. 7. 



A couple of narrow strips of the thinnest tissue paper, 

 hung upon a support, will behave similarly when electri- 

 fied. But the best results are obtained with two strips 

 of gold-leaf, which, being excessively thin, is much 

 lighter than the thinnest paper. The Gold-Leaf Electro- 

 scope is conveniently made by suspending the two leaves 

 within a wide-mouthed glass jar, which both serves to 



