its distance east or west of a given meridian, called its longitude. In measuring longitude, the meridian commonly used, called the prime meridian, is that of Greenwich, near London, England. The meridian of Washington is sometimes used.

Since the earth is practically a large sphere, distances on its surface are measured along arcs of circles, and hence are expressed in degrees, minutes, and seconds of arc.

To say that a place is in latitude 38° N. means that it is 38° north of the equator. And to say that a place is in longitude 117° E. means that it is 117° east of the meridian of Greenwich.

Exercises

1. By looking at a map, find the latitude and the longitude of each of the following: New Orleans; New York; Charleston, S.C.; Denver; Pekin, China; Lima, Peru; Rio Janeiro, Brazil; Cape Town, Africa.

2. The following table gives the longitudes, to the nearest minute, of twelve cities.

How far is it in longitude between Boston and San Francisco?

4. Find the difference in longitude between Chicago and Paris.

5. Find the difference in longitude between Boston and Manila.

6. How far is Cleveland west of London ?

7. How far is Tokio east of Calcutta?

8. Find the differences in longitude between other cities given in the above table.

Longitude and Time

1. How often does the earth turn on its axis? In what direction does it turn?

2. Make a point on a ball or globe, turn the globe on its axis, and discover the figure described by the point when the globe makes a complete revolution.

Table

The earth turns through 360° longitude in 24 hr. time 15° longitude in 1 hr. time 1° longitude in 4 min. time 15' longitude in 1 min. time 1' longitude in 4 sec. time

3. Through how many degrees does the point move? Through how many degrees of longitude does a point on the earth's surface move in 24 hours?

4. Since a point on the earth's surface moves through 360° in 24 hours, through how many degrees does it move in 1 hour?

Exercises

1. If your city is just passing under the sun, i.e. if it is just noon, has a point 15° west of you yet passed under the sun? When will it do so?

2. When you have noon, what time is it 15° west of you? What time 15° east of you?

3. When you have noon, what time is it 30° west of you? What time 30° east of you?

4. What time is it 71° west of you when you have noon?

5. When it is 10 A.M. in your city, what time is it 10° west of you? 40° east of you? 90° east of you?

6. When it is 1 P.M. in your city, what time is it 60° west of you? 105° west of you? 90° east of you?

7. When it is noon at Chicago, what time is it at Boston?

Hence it is 6 min. 16 sec. after 1 P.M. at Boston.

8. When it is noon at Chicago, find the time at San Francisco.

9. When it is 10 A.M. at Boston, find the time at Paris. 10. When it is midnight at Chicago, what time is it at Manila?

11. A boat race occurs on the Thames at 5 P.M. The result is known in Philadelphia at 1 P.M. Account for this.

12. When it is 5 A.M., October 22, at Manila, what time and what date is it at Boston?

17. STANDARD TIME

The time considered above is called local time. The fact that all places east of a given point have later local time, and all places west of it earlier local time, caused confusion in railroad travel. Hence, in 1883, the railroads of the United States adopted for their own convenience what is

known as standard time. At any particular place the time is reckoned as the local time of some specified meridian rather than the meridian through that place. The meridians used are 75°, 90°, 105°, and 120° west of Greenwich. Thus places within about 71° of any of these meridians use the local time of that meridian.

The line of division between standard meridians is not a straight line midway between them, but depends upon important railroad terminals. It was fixed by the roads. This is shown in the following map:

1. From what meridian do you reckon time in your town or city? Has the meridian (a north and south line) through your place passed under the sun before or after this meridian does?

2. Do you live east or west of the meridian from which you reckon time?

3. How many degrees is your meridian from this meridian? Compare your local time with the standard time.

4. Suppose one lives 7° east of the 90th meridian. Is standard time fast or slow? How much?

The local time of the 75th meridian is Eastern Time, of the 90th, Central Time, of the 105th, Mountain Time, of the 120th, Pacific Time.

6. When it is 8 A.M. Eastern Time, what is it Pacific Time?

7. When it is 4 P.M. Mountain Time, what is it Eastern Time?

8. At noon by Central Time, what is it by each of the others?

9. If one is traveling from New York to Chicago, how will he change his watch as he changes into Central Time? 10. When it is noon in Chicago, what time is it in New York? Charleston? New Orleans?

11. When it is 3 P.M. in San Francisco, what time is it in St. Louis? Detroit? Boston?

12. Make and solve other problems about standard time.

18. FOREIGN MONEY

The money used by people of other nations is different from that used in the United States. Americans who buy goods in a foreign country, or who travel in a foreign country, must know the value of the different denominations of money used in that country.

The following tables give the denominations of money used in some countries of Europe, together with their equivalents in the money of the United States.