CHAPTER XV.

287. What is the origin of the term electricity? What is said of attraction and repulsion in electricity?

288. What is the supposed explanation of electrical repulsion? Explain the difference between resinous and vitreous electricity. What is said of the two supposed electrical fluids? Detail the illustrations of attraction which are stated.

289. State the theory of Franklin. Explain the use of the terms positive and negative. Illustrate the fact that the kind of electricity excited depends on what a substance is rubbed with.

290. What is said of the incorrectness of the terms vitreous and resinous? What is said of conductors and non-conductors? Why are non-conductors called insulators?

291. What marked difference is there between heat and electricity? State the experiment represented in Fig. 258. What is said of electrics and non-electrics?

292. What is said of equilibrium in electricity, and of its disturbance? Give in full what is said of the universality of electricity.

293. State what is said of induction, as illustrated by the experiment represented in Fig. 259.

294. State the experiment represented in Fig. 260. Describe the arrangement and operation of the electrical machine represented in Fig. 261.

295. Describe the cylinder machine. State the experiment with the pith balls. State that with the head of hair.

296. State the experiment with the tissue-paper. State that with the dancing figures. State that with the bells.

297. Describe the experiment with the tin-foil. Describe the insulating stool and the operation of it.

298. What is said of the escape of electricity from points? Describe the apparatus represented in Fig. 269, and the operation of it. What is said of the discharge of electricity from a point in a dark room? Describe the Leyden jar.

299. Explain the operation of the Leyden jar. What would be the effect of connecting the inside foil with the outer by a strip of foil? Give in full the experiment represented in Fig. 272, and the explanation.

300. What is said of the discharge of the jar? How can a large number of persons take a shock from it together?

301. Explain the effect of moisture upon the charged jar. State the experiment represented in Fig. 274.

302. What is the electrical battery? What is said of the light produced by electricity?

303. To what is the report of electricity owing? What is said of mechanical injuries caused by electricity? What of the heat caused by it? What effects may be produced by this heat?

304. What was the discovery of Franklin, and how did he make it?

305. Relate the accident which occurred at St. Petersburg. What is said of lightning-rods?

306. What was Sulzer's experiment? What were Galvani's observations?

307. What is said of the pile of Volta? What of his cup battery and of other batteries?

308. What difference is there between frictional and voltaic electricity?