2 of the circumference of a circle. It varies, therefore, with the size of the circle. If the circumference of the earth at the equator is divided into 360 equal parts, one of these parts expresses a degree of latitude or longitude at the equator. It is about 69.16 statute miles, or 60 geographical miles. 1. How many degrees in C.? C.? C.? 24 C.? 5 C.? 36 2. Recite the table of circular measure. 3. How many degrees in 300'? 5400"? 180' ? 70'? 140'? 4. What part of a circumference is 180°? 90°? 30°? 45° ? 5. Define right angle; acute angle; obtuse angle. 6. How many degrees are there in 5 of a right angle? of a right angle? of a right angle? 7. What part of a right angle is 36°? 60°? 80°? 72°? Measure each of the following angles, and add the results. 8. 9. 10. Estimate each of the following angles by the eye, then test your answers with the protractor, noting the correct answers. 11. 12. LESSON 26 1. Reduce 81° 45' 28" to seconds. 2. Change 84,672" to higher denominations. 3. Find the sum of 24° 32′ 42′′, 64° 55′ 38′′, 75° 36′ 22′′. 4. From of 98° 25′ 24′′ take 9° 59". 5. Find the sum of 72.325°, 4.28', 29.5". 6. Multiply 14° 7' 18' by 6. 7. Divide 49° 17' 24" by 6. The Equator is a great circle midway between the north and south poles. Parallels are small circles parallel to the equator. They indicate the distance of places north or south of the equator. Meridian Circles are great circles extending through the poles of the earth, perpendicular to the equator and the parallels. They indicate distances east or west of some meridian taken as a standard. Meridian means middle of the day. In all places situated on the same meridian it is noon or midday at the same time. The position of a place on the earth is indicated: 1. By its distance north or south of the equator. 2. By its distance east or west of a standard meridian. Latitude is distance north or south of the equator measured along the meridians. It is reckoned in degrees. The latitude of any place on the equator is latitude 0°. Places north of the equator are in north latitude; those south of the equator south latitude. The latitude of the north pole is 90° N.; of the south pole 90° S. LESSON 27 Longitude is distance east or west of a standard meridian. It is reckoned in degrees. The meridian from which longitude is reckoned is called the standard meridian. Nearly all countries have adopted the meridian passing through Greenwich, near London, as the standard. Sometimes, however, it is reckoned from the capital of the country, as from Washington or Paris. The longitude of any place on the standard meridian is longitude 0°. Places not exceeding 180° east of the standard meridian are in east longitude; places not exceeding 180° west of it are in west longitude. Since there are only 180° in half a circle, the greatest value of longitude a place can have is 180°. The value of a single degree of longitude on the equator is equal to about 69.16 miles; at latitude 20° it is about 65 statute miles; at 30°, about 60 miles; at 40°, about 53 miles; at 80°, about 12 miles; at 90°, 0 miles. (See diagram, p. 35.) 1. What are the names of the lines that extend from east to west on the globe? What are the names of those that extend from the north to the south pole? 2. What is the equator? What are parallels? Meridians? 3. What is latitude? How is latitude measured and reckoned? What is the latitude of all places on the equator? What is the latitude of the poles? 4. What is longitude? How is it reckoned? 5. What is meant by standard or prime meridian? 6. What meridian has been adopted by nearly all countries as the standard? 7. What is the greatest longitude a place can have? 8. What places have no longitude? LESSON 28 ་ (Get answers from the diagram, p. 35.) 1. What is the latitude of A? Longitude? 2. State the latitude and longitude of C. 3. What is the latitude of B? What is the difference in latitude between A and B? 4. What is the difference in longitude between A and E? J and K? A and C? E and K? D and L? D and G? 5. What is the difference in latitude between B and C? C and J? 6. What is the latitude of I? 7. What is the latitude of M? Longitude? 8. What is the difference in latitude between D and H? 9. What is the difference in longitude between H and L? 10. The latitude of Washington is 38° 53′ 20′′ north, and of Richmond 37° 32′ 17′′ north. Find the difference in latitude. 11. The latitude of Savannah is 32° 1' north, and of Cincinnati 39° 6' north. What is the difference in latitude? 12. The latitude of New Orleans is 29° 57' north, and of Quito 13' south. Find the difference in latitude. 13. The latitude of New York is 40° 42′ 43′′ north, and of Rio Janeiro 22° 54' south. Find the difference in latitude. 14. Boston is 71° west of Greenwich. 3′ 58'', and Washington 77° 0′ 28'', What is the difference in longitude? 15. New York is 74° 0' 3", and Omaha 96°, west of Greenwich. Find the difference in longitude. 16. The longitude of St. Paul, Minn., is 93° 5' west, and of Marseilles, France, 5° 22' east. What is the difference in longitude? |