32. 3.36 T., 6.6139 T., .00992 T., 4.4092 T. Express in short tons : 33. 1.9684 long T., 6.8894 long T., .004921 long T. Express in troy pounds: 34. 5 lb. avoirdupois, 13.228 lb. avoirdupois, 6613.87 lb. avoirdupois. Express in avoirdupois pounds: 35. 7 lb. troy, 13.396 lb. troy, 5.358 lb. troy. 42. A lot is 40 by 120 feet. How many such lots make 40 acres? 43. How many barrels of 311 gallons each will a rectangular tank 12 ft. by 8 ft. and 5 ft. deep hold? (Allow 7 gal. to a cubic foot.) How 44. The weight of a half dollar is 12 grams. many half dollars can be made out of 7500 grams of standard silver? 45. Find the cost of boring an artesian well 1400 feet deep at $4 a linear foot for the first 900 feet, $4.50 per linear foot for the next 200 feet, $5 per linear foot for the next 100 feet, $5.50 per linear foot for the next 100 feet, and $6 per linear foot for the remainder. 46. The rails of the Great Western Railway, England, weigh 97 lb. per yard. Find in tons the weight of the rails required to construct 1 mile of this railway. = 47. Express in the ordinary decimal notation : 3.27 × 106, 17.45 × 109, 9.4 × 103, 7.3 × 106. 48. Given 10-1=16, 10-2 = 100, 10-8 = =10000, 10-5 =100000, 10-6 = 1000000. Express in the ordinary decimal notation : (a) 3.2 × 10-3, 4.71 x 10-6, 9.83 x 10-8. (b) 4.98 × 10-5, 9.371 × 10−6, 4.329 × 10-4. 1000, 10-4 LONGITUDE AND TIME A meridian is an imaginary line running due north and south from pole to pole. Longitude is the distance, expressed in circular arc measure, east or west from the prime or standard me ridian. The meridian through any particular place may be used as the prime meridian. The meridians through the observatories of Greenwich, Washington, Paris, Madrid, Rome, Stockholm, Pulkova, and Lisbon have been used as prime meridians by the nations to which these cities belong. The International Geodetic Congress, which met at Washington in 1884, recommended that the meridian passing through the observatory at Greenwich, a suburb of London, be the prime meridian. This recommendation is now generally adopted by the great nations of the world. The meridian of Greenwich is taken as prime meridian in this book. Longitude is reckoned in either direction halfway around the earth from the prime meridian. The greatest longitude a place can have is 180° E. or 180° W. The meridian 180° E. or 180° W. of the prime meridian is a continuation of the prime meridian on the other side of the earth, and forms with the prime meridian what is called a great circle passing through the poles. Con The earth rotates on its axis from west to east. sider two places not on the same meridian; for example, New York City and St. Louis. New York being farther east will come the sooner under the influence of the sun's rays. Therefore, when it is noon in New York City it is before noon in St. Louis. Since the earth's motion is uniform, and furthermore, since in 24 hr. the earth rotates 360°, .. in 1 sec. the earth rotates 15". A difference of 15° of longitude corresponds to a difference of 1 hr. of time. A difference of 15' of longitude corresponds to 1 min. of time. A difference of 15" of longitude corresponds to 1 sec. of time. Hence, to convert difference of longitude into difference of time, divide by 15. EXERCISE 97 1. When it is noon at London, what is the time at New Orleans, 90° W. ? 2. When it is 9 o'clock A.M. on the meridian 75° W., what is the time on the meridian 90° W.? 3. The longitude of Denver is 105° W. When it is 3 o'clock P.M. in Denver, what is the time in London? 4. Two places differ in longitude by 20°. What is their difference in time? 5. A person travels east 15°. What change must he make in the time indicated by his watch so that it may indicate local time? Supposing he goes the same distance west, what change must be made in the time indicated by his watch? 6. When it is noon in London, what is the longitude of the places in which it is 4 o'clock P.M.? 5 o'clock A.M.? 7. When it is 2 o'clock P.M. in Washington, what is the time in places 30° W. of Washington? in places 75° E. of Washington? 8. What is the difference in longitude between places which differ in time by 2 hr. 30 min.? by 4 hr. 10 min. ? 9. If a person travels from Denver to New York, will his watch be fast or slow when he reaches New York, and how much? 10. To how many hours does a difference of 80° in longitude correspond? 11. What difference in longitude corresponds to a difference of 4 hr. 20 min. in time? 12. A person living on the 90th meridian W. wishes to send a telegram to a bank in New York City, directing the bank to pay on the same day a sum of money. Up to what hour in the afternoon may he do this, allowing 30 minutes for the transmission of the telegram, taking the longitude of New York as 75° W.? (New York banks close at 3 P.M.) 13. At places on the same parallel of latitude the sun rises at the same instant local time. How many minutes. earlier does the sun appear to a person who travels 1o E.? |