sides that of ascertaining the probable change of the weather? *185. Required the density of the air at twenty-eight miles above the earth's surface. 186. Required the pressure of the atmosphere on six square inches of surface. 187. Required the weight of the atmosphere in tons. 188. If the atmosphere of Mars be twice as dense as that of the earth and reckoned as high, what will be its weight, supposing the diameter of Mars to be 4000 miles? 189. What difference would there be in the height of the quicksilver in a barometer at the top of the highest mountain in the world, to what it would be at the bottom of the mountain? WATER. 190. In what different states does water exist? 191. What is Steam or Vapour? 192. What is the simplest state of water? 193. Is ice heavier or lighter than water? 194. What are the component parts of water? 195. What was the opinion of the ancients respecting water? 196. Give proofs of the universality of water. 197. Which is the purest kind of water? 198. What are the opinions of philosophers relative to the sea's acquiring its saltness? 199. What part of the earth's surface does the ocean cover? 200. Is there any air in water? 201. What part of the ocean is the saltest, and why? 202. What causes the impurity of rain water? 203. Why is the Thames water preferred for long voyages? 204. Which putrefies soonest, spring water or river water? 205. What causes the hardness of spring water? 206. Where have springs of fresh water been discovered in the sea? 207. Which is most capable of being confined, water or air? 208. What is the boiling point of water when the barometer is at 29 inches, and when at 31 inches, and wha is the cause of the difference? 209. Where are the chief hot springs? 210. What is the mean specific gravity of water? 211. What causes the specific gravity of water to vary? 212. To what cause are Earthquakes and Volcanic eruptions assigned? 213. Which may be made to displace the greatest weight, a pound of gunpowder, or a pound of water? 214. What causes that motion of water called boiling? 215. Give an example of the surprising power of steamengines. 216. How much rarer than water is steam at 212°? 217. Explain the theory of boiling. 218. How many balls in a day of 16 hours would Perkins's steam-gun discharge, if it could continue with the same rapidity that it does in the first four seconds of its action? 219. Required the weight of a tun of water. 220. Required the weight of a cube of three feet of water. 221. What quantity of water might be thrown up by St. Winifred's well in a day of 24 hours? HYDROSTATICS AND HYDRAULICS. 222. Define Hydrostatics and Hydraulics. 223. How are fluids divided? 224. How do fluids press? 225. How much greater will be the pressure of a body of water of a cylindrical shape than of a body of a conical shape, provided their bases are equal? *224. Give an example of the astonishing effect that might be produced by the perpendicular pressure of a small body of water. *225. What causes the sides of canals to be sometimes blown up? 226. What is meant by Specific Gravity? 227. In reference to what other body is the specific gravity of bodies given? 228. If a body sink in a fluid, what quantity of the fluid will it displace? 229. If a body swim in a fluid, what quantity of the fluid will it displace? 230. What is the name of that instrument by which the specific gravity of bodies is ascertained?. 231. How is the specific gravity of a body that swims in water ascertained? 232. How is the specific gravity of a body that sinks in water ascertained? 233. Had the ancients a knowledge of Hydraulics? 234. How did the ancients convey water from the top of hill, or other elevated place, to the top of another hill? 235. To what science does the construction of mills belong? 236. Why cannot water be raised in a sucking pump beyond a certain limited height?* 237. Describe the Sucking Pump. 238. Describe the Forcing Pump. 239. Is the height limited to which water may be thrown by a forcing pump? 240. Describe the Siphon. * It is necessary here to make an observation or two, in order to rectify an apparent incongruity at two different parts of this work, relative to the height at which water may rise in a pump. Under the article Hydraulics, it is stated that a column of air, of the height of the atmosphere, will counterbalance a column of water of about 32 or 33 feet high; while under Pneumatics, the column of water capable of being suspended, is stated to be about 34 or 35 feet. To explain and reconcile these two statements, it must be remembered that the height of the water in the pump must depend on the weight, or pressure, of the atmosphere: now it is well known, that in our climate the range of the barometer is between 28 and 31 inches; consequently, the dif. ference will be proportionately great in the range of the water in the pump. When the barometer is at 28, the height of the water capable of being counterbalanced will be 31'6; when the barometer is at 31, the water may be 35 feet high. In practice, water is seldom raised much above 28 feet. 241. Why must the siphon be exhausted of air before it will act? 242. Why will not the siphon act, when the longer leg is immersed in the liquor that is to be drawn off? 243. On what principle are Fire Engines? 244. If a body weigh 74 grains in air, and 68 in water, what will be its specific gravity? 245. If a body weigh 136 grains in air, and 120 in water, what will be its specific gravity? *245. If a tube of one inch bore, and 30 feet high, be inserted into a cask of water, whose base is one foot in diameter, what will be the pressure if the tube be filled with water? 246. If it were possible that the quicksilver could rise in a barometer to 40 inches, of what height would be the column of water that might be counterbalanced by it in a pump? ACOUSTICS. 247. Of what does Acoustics treat? 248. Is air the sole transmitter of sound? 249. Define Sound. 250. On what does the intensity of sound depend? 251. What difference is there in the intensity of sound, conveyed by hydrogen gas, and by carbonic acid gas? 252. What is the name of that nerve which conveys sound to the brain? 253. Is the ear the only means by which sound may be conveyed to the brain? 254. What effect has the state of the atmosphere in regard to sound? 255. Required the number of vibrations in a second, to produce the most acute and the most grave sound. 256. Which travels quickest, the human voice, or the report of a cannon ? 257. At what rate per second does sound travel? 258. How may the distance of a thunder-storm be calculated? 259. Give an example of the conducting power of water? 260. At what rate does sound travel in water? 261. In what do sound and light resemble each other? 262. Which is the best conductor of sound, brick or stone? 263. What is an Echo? 264. Why can a person in the whispering-gallery of St. Paul's, hear another distinctly, if he speak in a whisper on the opposite side? 265. Why are the repetitions of an echo more numerous in the night-time than in the day? 266. Describe the Speaking Trumpet. 267. Describe the Invisible Girl. 268. Required the distance of a thunder-cloud, if a space of thirty seconds intervene between the lightning and the thunder. 269. Heard the report of a gun from a ship at sea, when just twelve seconds before, the flash was seen; required the distance of the ship. 270. What space of time will intervene between the flash and report of a piece of ordnance fifteen miles distant? 271. If I hear the echo of my voice from a building just eight seconds after I speak, at what distance will the building be from me? METEOROLOGY. 272. What is Meteorology? 273. How high does the atmosphere extend? 274. What is the average quantity of aqueous vapour contained in the atmosphere? 275. How much lighter than water is the atmosphere? 276. Through what means is it that water is suspended in the atmosphere? 277. What quantity of water is supposed to be taken up annually by the atmosphere? 278. What quantity is carried off by evaporation from the Thames in a summer's day, and what quantity from the Mediterranean in the same time? |