281. What is said of the recomposition of decomposed light? Give the illustration of the powder--the circular board--the top. 282. What is said of the colors of substances? What of the variations of these colors in different lights? What of variations with varying positions? What of the colors of clouds? 283. Explain the formation of the first rainbow by Fig. 253. Explain the formation of the second bow by Fig. 254. 284. What is said of the circumstances under which rainbows are seen? 285. Explain in full the formation of the two bows as illustrated by Fig. 255. What is said of the bow as seen by different persons, and at different moments by the same person? What of rainbow hues in dew-drops and ice-crystals? 286. Give the dissection of light as represented in Fig. 256. What is said of Daguerreotyping? 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?