LUSSONS IN ELECTRICITY. 



611 



tubing, and flannel and silk rubbers before a lire, to insure their dry- 

 ness. Be specially careful to make your glass tubes and silk rubbers 

 not only warm, but hot. Pass the dried flannel briskly once or twice 

 over a stick of sealing-wax or over a gutta-percha tube. A very small 

 amount of friction will excite the power of attracting the suspended 

 straw, as shown in Fig. 2. Repeat the experiment several times and 

 cause the straw to follow the attracting body round and round. Do 

 the same with a glass tube rubbed with silk. 



I lay particular stress on the heating of the glass tube, because 

 glass has the power, which it exercises, of condensing upon its surface, 

 into a liquid film, the aqueous vapor of the surrounding air. This 

 film must be removed. 



I would also insist on practice, in order to render you expert. You 

 will, therefore, attract bran, scraps of paper, gold-leaf, soap-bubbles, 

 and other light bodies, by rubbed glass, sealing-wax, and gutta-percha, 

 Faraday was fond of making empty egg-shells, hoops of paper, and 

 other light objects, roll after his excited tubes. 



It is only when the electric power is very weak that you require 

 your delicately-suspended straw. With the sticks, tubes, and rub- 

 bers here mentioned, even heavy bodies, when properly suspended, 

 may be attracted. Place, for instance, a common walking-stick in the 

 wire loop attached to the narrow ribbon. Fig. 1, and let it swing hori- 

 zontally. The glass, rubbed with its silk, or the sealing-wax, or gut- 

 ta-percha, rubbed with its flannel, will pull the stick quite round. 



Fig. 4. 



Abandon the wire loop ; place an q^^ in an egg-cup, and balance 

 a long lath upon the Q^g, as shown in Fig. 4. The lath, though it 

 may be almost a plank, will obediently follow the rubbed glass, gutta- 

 percha, or sealing-wax. 



Nothing can be simpler than this lath and e^^ arrangement, and 

 hardly any thing could be more impi-essive. The more you work with 

 it, the better you will like it. 



Pass an ebonite comb through the hair. In dry weather it* pro- 

 duces a crackling noise ; but its action upon the lath may be made 



