ELECTRICITY. 855 



The Spider seemingly animated by Electricity. 



Fig. 9 is an electric jar, having a wire C fastened 

 on its outside, which is bent so as to have its knob 

 E as high as the knob A of the jar. B is a spider 

 made of cork, with a few short threads run through 

 it, to represent its legs. This spider is fastened at 

 the end of a silk thread proceeding from the 

 ceiling of the room, or from any other support, so 

 that the spider may hang midway between the two 

 knobs A, E, when the jar is not charged. Let 

 the place of the jar upon the table be marked; 

 then charge the jar, by bringing its knob A in con- 

 tact with the prime conductor, and replace it in 

 its marked place. The spider will now begin to 

 move from knob to knob, and continue this motion 

 for a considerable time, sometimes for several 

 hours. 



The inside of the jar being charged positively, 

 the spider is attracted by the knob A, which com- 

 municates to it a small quantity of electricity; the 

 spider then becoming possessed of the same elec- 

 tricity with the knob A, is repelled by it, and runs 

 to the knob E, where it discharges its electricity, 

 and is then attracted by the knob A, and so on. 

 In this manner the jar is gradually discharged, and 

 when the discharge is nearly completed, the spider 

 finishes its motion. 



To prove that Glass and other Electrics become Con- 

 ductors when they are made very hot. 



In order to ascertain the conducting quality of 

 hot resinous substances, oils, &c. bend a glass tube 

 in the form of an arch, C D (Plate 20. fig. 8.), 



a a 2 



