« PreviousContinue »
Force of gravity? Figure? Describe its seasons. Upon what does the change of seasons in any planet depend?
178. The appearance of the sky? The telescopic features? Are Jupiter's moons visible to the naked eye?
179. How named? What is their size? What space do they occupy?
180. Describe the eclipse of the moons.
181. Define immersion, emersion, and transit. How rapidly do the satellites revolve? What can you say of the frequency of eclipses on Jupiter? Describe the belts. Why are they parallel to its equator?
182. How was the velocity of light discovered? SATURN.—Definition and sign? Describe its appearance.
How rapidly does it move through the sky? (1869. * is in ui). Its distance from the sun? Peculiarity of its orbit?
184. Velocity? Year? Day? Distance from the earth? Diameter? Volume? Density? Force of gravity? Describe its seasons.
185. Has it any atmosphere? Who discovered the rings of Saturn? Describe them.
186. Are they stationary? Explain their phases.
187. Describe Saturn's belts.
188. Describe Saturn's moons. The scenery on Saturn. URANUS.TMDefinition and sign? How was it discovered?
Tell of its previous discovery by Le Monnier. Is Uranus visible to the naked eye? (1869. W is in 035). Distance from the sun? Year? Diameter? Density?
191. Describe its seasons. Telescopic features. Satellites Peculiarity of its moons.
Neptune.—Definition and sign? Appearance in the sky? Give an account of its wonderful discovery.
193. What is its distance from the sun? Year? Velocity? Diameter? Volume? Density? Do we know anything of the seasons? Why not? Intensity of the light?
194. Appearance of the heavens? What are the telescopic features? Has Neptune any moon? What advantage have the Neptunian astronomers?
Meteors, Aerolites, And Shooting-stars.—Define an aerolite. A shooting-star. A meteor. Give some account of the fall of meteors (aerolites).
197. What elements are found in aerolites? How can an aerolite be distinguished? Give an account of wonderful meteors.
198. Of shooting-stars.
199. Describe the showers of 1799 and 1833.
200. The shower of 1866. At what intervals did these showers occur? Why was not the shower of 1866 seen in this country t Ans. Our side of the earth was not turned toward the meteors.
201. What is the average number of meteors and shootingstars daily? Why do we not see more of them?
202. In what months are they most abundant? Describe the origin of meteors and shooting-stars. What is their velocity? What causes the light? The explosion often heard? What is said of a companion to our moon?
203. What is the theory of meteoric rings? What is their shape? How do these account for the showers at regular in tervals?
204. What is the period of the November ring? Why is the August shower so uniform, while the November one is only periodic?
205. What is the relation between meteors and comets? What do you mean by the radiant point? What effect do meteors have on the weather?
206. What is their height? Weight?
COMETS.—How were they looked upon by the ancients? Illustrate. Define the term comet. What is the tail? The nucleus? The head? Thecoma? Does each comet necessarily possess all these parts? How would a mere round, fleecy mass be known to be a comet? What mistake did Herschel make in looking, as he supposed, at one of this kind (p. 189)?
208. Where do comets appear? In what direction do they move? How does a comet look when first seen? Upon what does the time of greatest brilliancy depend? What do you say of the number of the comets? What was Kepler's remark?
209. Why do we not see them oftener? Where did Seneca see one? Describe the orbits of comets. Which class has been calculated? Which classes never return?
210. Describe the difficulty of calculating a comet's orbit.
211. Name the periods of some. What has been the distance from the sun of some noted comets? Velocity?
212. What do you say of the density of a comet? Illustrate. Is there any danger of our running against a comet?
213. Do comets shine by their own or by reflected light? Tell what you can of their variation in form and dimensions.
214. Give some account of the comets of 1811, 1835, and 1843. For what is Encke's comet noted? What is its period? Give some description of Donati's comet.
Zodiacal Light.—Where can this be seen? What is its appearance? Where is it brightest? What is its origin?
IIL—-the Sidereal System.
Tell something of the appearance of the heavens at Neptune's distance from the sun—our starting-point? Do we ever see the stars? What do we see, then?
222. Which star is nearest the earth? What is its parallax? Its distance? What is Prof. Airy's remark?
223. How long would it take light to reach the nearest star? How would the earth's orbit appear at that distance? Our sun? How long does it take for the light of the smaller stars to reach the earth? What can you say of the motion of the fixed stars? Illustrate.
224. What proof have we that the stars are suns? ("If Sirius shines as brightly as our sun, at its distance, it must be three thousand times larger."—Lockyer. ) That our sun is only a small star? Describe the motion of the solar system. What is the centre? How many stars can we see with the naked eye? With a telescope? Have all the stars been discovered?
226. What is the cause of the twinkling of the stars? Do the stars twinkle in tropical regions? Why not? What do you say of the magnitude of the stars? Name four points of difference between a planet and a fixed star.
227. What do you mean by a star of the first magnitude? How many are there? Of the second magnitude? How many sizes may one see with the naked eye? With a telescope? What is the cause of the difference in the brightness of the stars? What can you say of the names of the stars?
228. What can you say with regard to the division of the stars into constellations? Is there any real likeness to the mythological figures? Name any figure which seems to you well founded.
229. Are the boundaries distinct? Who invented the system? Give the meaning of the signs of the Zodiac and their origin.
230. Explain why the signs and constellations of the Zodiac do not agree.
231. What causes the appearance of the constellations? Would they appear as they now do, if we should go out into space among them?
232. Are the present forms permanent? State the value of the stars in practical life.
233. What were the views of the ancients with regard to the stars?
234. Describe the division of the stars into three zones, and name them.
The Constellations.—The questions on these are uniformly: (1) description, (2) principal stars, and (3) mythological history. They need not therefore be repeated with each constellation.-—What are the pointers? Does Polaris mark the exact position of the North Pole? How many times per day is Polaris on the meridian of any place? Explain how this applies in navigation or surveying. State how the amount of the variation from the true north will change through the ages. What star will ultimately become the pole-star? What curious facts are stated concerning the Pyramids? What do you say of the distance of Polaris? How may latitude be calculated by means of Polaris?
Double Stars, Etc.—Does any star appear double to the naked eye? How many have been found by the use of the telescope? What is an optical double star? Are all double stars of this class? Describe the revolution of a binary system. What other combinations have been discovered? Their periods?
266. Orbits? Mass? Are these companion stars as close to each other as they seem? What can you say of the colored stars? Do their colors ever change? Which colors would indicate the hottest star?
267. What is the probable effect in a system having colored suns? What are variable stars? Describe the changes of Algol.
268. Of Mira. What is the cause? What are temporary stars? Describe the one seen in Cassiopeia.
269. The one in Corona Borealis, in 1866. What are lost stars?
270. Can you give any explanation? Of what did the star of 1866 consist? Are these stars destroyed? Is the process of creation now complete?
271. What are star clusters? Name several.
272. Is such a grouping a mere optical effect? Are they probably as closely compacted as they seem to be? What are nebulae? How do they differ from clusters? Is it probable that all nebulae will be resolved into clusters? What has spectrum analysis proved some of the nebulae to be?
273. Are they suns? Where are they most abundant? What can you say about their distances? Into how many classes are they divided? Describe and illustrate the elliptic nebulae. What is said of the distance of the great nebula in Andromeda? The number of stars it contains? Describe the annular nebulas. What is said of the "ring universe" in Lyra?
276. Its diameter? Describe the spiral nebula in Canes Venatici. Describe the planetary nebulae. What is said of the number and size of these "island universes?"
277. Describe the fantastic appearance of the irregular nebulas. What are nebulous stars? What is the cause?
278. What is said of the size of the one in Cygnus? What are variable nebulae?
279. Give instances. What is said of double nebulae? Is anything definite known with regard to them? What are the Magellanic clouds?
280. Describe the Milky-way. What can you say of the number of stars in the Galaxy? Are the stars uniformly distributed?
281. What is Herschel's theory of the constitution of the universe? If this theory be true, what is our sun?
282. Give an account of the Nebular hypothesis. What is said of Saturn's rings? May they ultimately disappear?
284. What is spectrum analysis? Name the three kinds of spectra.
285. What colored rays will a flame absorb? Describe the spectroscope.
286. What are Fraunhofer's lines? What is known of the constitution of the sun? What proof have we that iron exists in the sun?
287. What elements have been found in the sun? What proof have we that the stars are suns? What can you say of the similarity existing between the stars and our earth?
288. What has been discovered with regard to the constitution of the Nebulae? Of their relative brightness?
Time.—What two methods of measuring time? What is a sidereal day?
289. What are astronomical clocks? Tell how they are used. Why do astronomers use sidereal time? What is a solar day? What causes the difference between a sidereal and a solar day? To how much time is a degree of space equal?
290. Which is taken as the unit, the solar or the sidereal day? How long is a solar day? A sidereal day? A solar day equals how many sidereal hours? A sidereal day equals how many solar hours? Describe mean solar time. What is apparent noon? Mean noon? The equation of time? When is this greatest? When least?
291. When do mean and apparent time coincide? Can a watch keep apparent time? How may apparent time be kept?