point passes through 360° in one rotation of the earth on its axis. Since 360° of longitude pass under the sun's vertical rays during 24 hours, how many degrees pass during 12 hours? 1 hour? Since of 360° or 15° pass under the sun's rays in 1 hour, then 1 hour of time corresponds to 15° of longitude. Since 15° of longitude correspond to 1 hour of time, of 15° or 1°, or 15' of longitude, correspond to 1 minute of time, and 15" of longitude to 1 second of time. Table of relation between longitude and time: 360° of longitude correspond to 24 hours of time 1° of longitude corresponds to 4 minutes of time 1' of longitude corresponds to 4 seconds of time When the sun's rays are vertical on the 90th meridian, all places on that meridian have noon. The rotation of the earth from west to east makes the sun appear to move from east to west. The Mercator's map on p. 275 shows that when it is noon at Greenwich, it is before noon or earlier at all places west, because the sun's rays are not yet vertical on any meridian west of the prime meridian. It is after noon or later at all places east, because the sun's rays have already been vertical on all meridians east of the prime meridian. Examine the map. What time is it on the meridian of Greenwich? 45° east of Greenwich? 45° west of Greenwich? In traveling from London to New York would a watch be set forward or backward? about how much? About how much change in time must be made in traveling from Cal What is the difference in degrees between a place 30° east longitude and a place 45° east longitude? What is the difference in time and which has the earlier time? Written Work 1. When it is noon, solar time, at Paris, what is the solar time at New York? 2° 20' 15" E. 74° 0' 03" W. 15)76° 20' 18" 5 211" 5° 5 hr. 5 min. 21 sec. Since the earth rotates 15° in 1 hr., 15' in 1 min., and 15′′ in 1 sec., the difference in time is as many hours, minutes, and seconds as there are degrees, minutes, and seconds in of the difference in longitude. The difference in time is 5 hours, 5 minutes, 21 seconds. Since New York is west of Paris, the time in New York is earlier; that is, when it is noon at Paris, it is 6 o'clock, 54 min., and 38 sec. A.M. at New York. What is the difference in longitude between the two places? the difference in time? In going west from Paris to New York would a traveler set his watch forward or backward? how much? NOTE.-Study this diagram and make a similar one for each problem. Find difference in degrees, difference in time, and which place has earlier time: When the sun's rays are vertical on the meridian of Washington, find the solar time in the following places : 21. When it is midnight (solar time) on the last day of the year in Boston, how much of the old year (solar time) remains to the people of Honolulu ? 22. The first shock of the earthquake at Kingston, Jamaica (long. 76° 47′ W.), Jan. 14, 1907, occurred at 3:25 P.M. What was the solar time at New York? at Cape Town? 23. A ship sets sail from Liverpool for New York, Jan. 10, 1907. When in longitude 34° 6' 10" W. its chronometer reads 2:30 P.M. Jan. 15. Find the difference in the readings between the ship's time and the meridian time of New York. 24. Berlin meridian time is 6 hr. 44 min. and 11 sec. later than Chicago meridian time. Find the longitude of Berlin. 15 times the difference in time expressed in hours, minutes, and seconds corresponds to the difference in longitude expressed in degrees, minutes, and seconds. Therefore, 15 × 6 hr. 44 min. 11 sec. corresponds to 101° 0′ 26′′ of longitude. This difference in longitude would not tell us whether Berlin is east or west of Chicago, but as Berlin has faster time than Chicago, it must be east of it. Chicago is 87° 36′ 42′′ west of the prime meridian. Therefore, Berlin must be 13° 23′ 44′′ east of the prime meridian. 25. The "Treaty of Portsmouth" between Japan and Russia was signed at Portsmouth, N.H., Sept. 5, 1905, at 47 minutes past 3 P.M., 75th meridian time. What was the corresponding solar time at St. Petersburg, Russia, 30° 17′ 51" E. and at Tokyo, Japan, 139° 44′ 30′′ E.? Tokyo is east of the 75th meridian 214° 44′ 30′′, therefore its time is 14 hr. 18 min. 58 sec. faster than Portsmouth, which has 75th meridian time. Counting this time forward from 3:47 P.M. Sept. 5, gives 5 minutes and 58 seconds past 6 o'clock A.M. Sept. 6, Tokyo solar time. 26. The President of the United States takes the oath of office at 12 noon, 75th meridian time. Find the solar time and date in each of the following places for the inauguration of March 4, 1909: Honolulu; Berlin; San Francisco; London. International Date Line The nations have agreed upon the 180th meridian, with slight changes as shown on page 275, as the place where the new day always begins. The calendar is set forward one day on ships crossing this line sailing westward: the calendar is set back one day on ships crossing this line sailing eastward. 1. A ship sets sail from San Francisco for Manila, Oct. 9, 1906, at 9 A.M., 120th meridian time; it arrives at Manila, Oct. 27, at 9 A.M., meridian time. How long is the voyage? 2. The same ship sets sail from Manila, Nov. 3, 1906, at 3 P.M., meridian time, and arrives at San Francisco, Nov. 23, at 3 P.M., 120th meridian time. How long is the voyage? Standard Time The railroads of the United States in 1883 agreed upon a system of standard time and divided our country into four time belts, as shown on the map. In the eastern time belt all trains keep the time of the 75th meridian, known as |