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Regents' Questions and Answers

Physical Geography Friday, January 20, 1922. 1. How does a navigator determine his location (a) in the daytime, (b) at night, (c) when it is cloudy ? Ans. (a) By his latitude and longitude. The latitude may be found on any clear day by finding the altitude of the sun at its meridian and then adding or subtracting the sun's angular distance from the equator for the given day, as it is shown by the nautical almanac. The longitude may be found by comparing the sun time with Greenwich time, as it is shown by a chronometer. (b) By observing the moon and certain fixed stars. The altitude of Polaris will give the latitude in the northern hemisphere. (c) Location can not be found when it is cloudy. 2. Explain how rotation (a) causes the earth to bulge at the equator, (b) causes bodies to weigh least at the equator. Ans. (a) The theory is held that when the earth was in a molten state, the centrifugal force of rotation caused the bulging out and that it has become permanent by the further cooling of the earth. (b) The particles of the earth move faster at the equator and the tendency to fly off is greater than elsewhere. The centrifugal force acts to lessen the force of gravity, hence the weight is less. 3. Compare as to size the sun, the earth and the moon. Give the approximate distance of the earth from the sun and of the moon from the earth. Why do these distances vary 2 Ams. The diameter of the sun is 866,500 miles, or 1091% times that of the earth. The diameter of the earth is about 7,820 miles. The diameter of moon is 2,163 miles. The approximate distance (a) of the earth from the sun

is 92,975,500 miles, (b) of the moon from the earth is 238,840 miles.

4. How may it be proved that the air has weight? Mention four other important properties of the air as a whole, giving an application of each property.

Ans. It can be shown that the air has weight by first weighing an electric light lamp whose interior is a vacuum and then pierce the lamp to allow the air to enter. Weigh the lamp together with the broken glass if any and the increased weight will be that of the air let into the lamp. Air is elastic as in automobile tires. Air (a) offers resistance to a body passing through ; (b) is transparent, so that it may be seen through, and (c) is mobile, so that currents are produced in it.

5. In what essential particular in its construction does the principle of the mercurial barometer differ from that of the ameroid 2 Why does the barometer fall when carried up into the air How is this fall used in determining altitudes?

Ams. A mercurial barometer indicates the weight, or pressure, of the atmosphere by the height to which the air will raise a mercury column in a Torricellian tube, while the aneroid barometer indicates pressure by the amount of air pressure on the sides of a circular chamber within the aneroid thermometer. The atmospheric pressure decreases with the elevation above sea-level. Since the decrease of pressure is about onetenth inch for every 90 feet of rise, we are able to compute the elevation.

6. The southeast coast of Brazil is wet while the western coast of South America in the same latitude is dry; explain this difference. The Panama Canal Zone has summer rains whereas California has winter rains; explain.

A ms. The principal mountains of South America are in the western part. This permits the moist, southeast winds from the Atlantic to blow far inward over the continent until they reach the cool mountain barriers where rain is precipitated freely. The winds deprived of moisture pass over to the west coast, leaving it dry. The difference is explained by the northern movement of the heat equator during the summer months. 7. Using a diagram, explain the shifting of the wind from the northeast through the north, northwest and west to the southwest at New York ( 'ity.

What is the probable succession of

weather changes accompanying this

shift 2 A ms. Diagrams can not be given. The

probable succession of weather will be warmer with increasing cloudiness, followed by rain or snow ; then cloudiness followed by a cooler, clearing weather. 8. What is a tidal wave 2 What is meant by ebb tide' Mention two facfors effective in determining the height of the tide at any place or time. A ms. When an earthquake occurs near the sea, the water at first recedes from the land, this is followed by a great wave that advances many times inward to a great distance over the land. Such waves are called tidal waves. When the tide is running from the land back into the open ocean, it is called chb tide. The relative positions of the sun, moon and earth and obstructions to the tidal current as its entrance into a broad mouthed bay that narrows afterwards. 9. Floating objects set adrift on the coast of Florida may later be found on the western coast of Africa, carried there by the ocean currents; describe the route taken and name the currents involved. Explain the climatic influence of these currents on the lands washed by them. Ams. The floating object may be car

ried northeast by the Gulf Stream and then caught in the North Atlantic Eddy which carries the object to the west coast of Africa. Ocean currents give heat and moisture to the winds passing over them and thus modify the climate of lands washed by them. Cold currents cause a cool, dry climate. 10. Describe the source and the character of the deposits forming on the different parts of the ocean bed. By what process do these deposits become a part of the land 2 Name three classes of rocks formed from these deposits. Ams. The near shore deposits consist of sand, gravel and mud beds. The gravel beds are nearest shore and the mud beds are the most remote. Limestone is often found in clear waters beyond the mud beds. Limestone consists of the ground shells of sea animals, while the other rock are formed by the crushing of former rocks by water in motion. An uplift of the ocean bed joins these deposits to the land. Sandstones, limestones and shales are the rocks formed from these shore deposits. The deep sea deposits consist of red clay. 11. Name three active agents of erosion of the land, giving ome locality where each is dominant. What is meant by the base level of erosion? Explain another process by which the height of the land is lowered. Ams. Rivers, glaciers, waves. Greenland is covered with a vast glacier. The level beyond which no part of a stream may deepen its bed is called the base level of erosion. The Colorado basin is a region of erosion by rivers; south coast of England is eroded by waves. The heighth of land is lowered by gradual sinking of a region. 12. Give four means of identifying minerals. IIow may one distinguish (a) calcite from quartz, (b) mica from gypsum, (c) garnet from ruby ?

A ms. By its cleavage, its hardness, its luster and its chemical composition. (a) Quartz has no cleavage, is very hard so as to scratch glass and is slightly soluble in water. Calcite has cleavage in three directions, is soft and quite soluble in water. (b) Mica splits into thin, tough elastic sheets; while gypsum splits into thin, non-elastic flakes. (c) Garnet is a crystallized form of feldspar varying in color, while the ruby is a red crystallized form of corundum. 13. What is the explanation of stratification in rocks? Name two classes of rocks that are stratified and ome class that is unstratified. How may one account for fossils in rocks 2

Ans. The stratification was caused by a pause or a change in the character of

the rock material deposited as from mud

to sand. Stratified rocks are deposited from water but the winds blow sand into stratified structure. Igneous rocks are generally unstratified when they cool from melted state. Fossils are remains of animals and plants mingled with rock material.

14. Why are lakes more numerous in Minnesota than in Kentucky? How are lakes extinguished 2 Explain how Great Salt Lake has developed from the condition of a fresh water lake.

Ams. Minnesota was originally a region covered by a glacier and on melting the glacial streams became choked forming numerous lakes. Lakes are extinguished by decreased rainfall and by the removal of some obstruction at their mouth. Great Salt Lake has become salt owing to the fact that evaporation of its waters exceeds the quantity of water received by it.

15. Relate briefly the differences discovered in a comparative laboratory study of the Maine and the New Jersey shore lines, or of a region in youth and a region in maturity, or of a young river

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