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The longitude of Constantinople is
The longitude of Sitka is

The sum is
The difference in longitude, then, is

28° 59' east
135° 20' west
164° 19'
164° 19'

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Due to the rotation of the earth and the division of the equator into 360 degrees, the sun apparently passes over 24 of 360° or 15o each hour. Similarly it appears to pass over 1° every 4 minutes.

Rule. - To find the difference in time in minutes, multiply by 4 the number of degrees difference in longitude.

Rule. - To find the difference in longitude in degrees, divide by 4 the number of minutes difference in time.

EXAMPLE 1. Find the difference in time between Boston and San Francisco if the difference in longitude is 51 degrees.

51, difference in longitude

4 204 minutes, or 3 hr. 24 min., difference in time

EXAMPLE 2. Find the difference in longitude between London and New York if there is a difference in time of about 5 hours.

5 hours is 300 minutes 75, the number of degrees difference in longitude 4 300 minutes difference in time

Exercise

1. Through how many degrees does the earth turn in 1 hour ? in 5 hours ?

2. When it is noon at Washington, what time is it at a place 15° 30' east of Washington ? 45° 45' west?

3. What is the difference in longitude between two places whose difference in time is 1 hour, 10 minutes ?

4. If a person travels until his watch is 2 hours fast, in what direction and through how many degrees has he traveled ?

5. What is the difference in time between two places whose longitudes are 75° east and 60° east? 75° east and 60° west ? 75° west and 60° west ?

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Antwerp
Berlin
Boston
Buenos Aires
Capetown.
Chicago
Constantinople
Denver
Havana
Honolulu
Manila .
Mexico City

LONGITUDES OF VARIOUS CITIES

4° 25' E. Naples
13° 24' E. New York
71° 04' W. Panama
58° 22' W. Paris
18° 29' E. Pittsburgh
87° 37' W. Rome
28° 59' E. San Francisco
104° 59' W. St. Louis

82° 22' W. Sydney .
157° 52' W. Tokyo
120° 58' E. Valparaiso
99° 07' w. Washington

14° 14' E. 74° 00' W. 79° 32' W.

2° 20' E. 80° 03' W. 12° 29' E. 122° 25' W.

90° 12' W. 151° 12' E. 139° 44' E. 71° 39' W. 77° 03' W.

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Exercise
Using the above table answer the following:

1. When it is noon at San Francisco what time is it at Antwerp? at Berlin ? at Boston ? at Buenos Aires ?

2. When it is noon at Constantinople what time is it at Capetown? at Chicago ? at Denver? at Havana ?

3. When it is 6 A.M. at New York what time is it at Honolulu ? at Manila ? at Mexico City ? at Naples ?

4. When it is 3 P.M. at Panama what time is it at Paris ? at Pittsburgh ? at Rome? at San Francisco ?

5. When it is midnight at Washington what time is it at St. Louis ? at Sydney? at Tokyo? at Valparaiso ?

Standard Time

For practical purposes a great part of the civilized world is now divided into sections, all places in the same section using the time of a certain meridian in that section. To make the times of adjacent sections just one hour apart, the meridian usually chosen is 15°, 30°, 45°, or other multiple of 15°, east or west of the meridian

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MAP SHOWING TIME OF DIFFERENT LOCALITIES AT A DEFINITE MOMENT

through Greenwich. Thus, England uses the time of Greenwich, that is, 0°; Central Europe uses that of 15° E.; Japan uses that of 135° E.; and the Pacific Slope of the United States that of 120° W.

A time system where all places in a section of territory near some chosen meridian have the same time is called a system of standard time. The standard time map of the United States is shown on the following page.

The irregular boundaries of the sections are due to a

Detroit Cleeland Hartford

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oCharlestoy thapolis PACIFIC TIME

MOUNTAIN TIME CENTRAL TIME
120

EASTERN TIME
105
90

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de St. Paul
Pierre

Madison

Lansing
Omaha

of Trenton
Topeka Springfieldo 10

Frankfort Richmond
Nashville

Raleigbo

Greenyille
Little Atlanta
Rock Montgomery

desire to have the division lines pass through important railway centers.

When it is noon by Eastern time it is 11 A.M. by Central time.

When it is noon by Eastern time it is 10 A.M. by Mountain time.

When it is noon by Eastern time it is 9 A.M. by Pacific time.

Olympian Portland

o Salem

seattle

Helena
Butte

Bismark

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Minneapolis

Cheyenne

Albanyo Boston

Carson City

Sacrainento
San Franci&co

Ogder
Salt Lake
City:

Denver

-N.Platte
McCook

Broken Des Moines

icago, Toledo Lincoln

Indianapolis

Pittsburgh New York Columbus

Dover

Urada

Dodge City

Liberal

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Kansas City,
Jefferson

City

Ashfork

Phoenix

St. Louis

Santa Fe

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Oklahoma

Columbia

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105

90

75

STANDARD TIME MAP OF THE UNITED STATES

Exercise
In the following examples use the above map.

1. When it is noon in California what time is it in Vermont? in Kentucky? in Wyoming ? in eastern Arizona ?

2. When it is 6 P.M. in Massachusetts what time is it in Michigan ? in Oklahoma ? in Utah ? in Florida ?

3. When it is midnight in Iowa what time is it in Montana ? in Washington ? in Ohio ? in New York ?

4. When it is 6 A.M. in Maine what time is it in Alabama ? in Minnesota ? in Oregon ? in Virginia ?

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5. When it is 9:30 A.M. in Colorado what time is it in Florida ? in Pennsylvania ? in California ? in Texas ?

6. An order from San Francisco to Boston is wired at 2 P.M. The wire takes i hr. to reach Boston, where the office of the recipient closes at 6. Will the telegram be received before closing time?

Board and Lumber Measure

The board foot is the unit used in measuring lumber, and is the amount of lumber in a piece one foot wide, one inch thick, and one foot long.

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Rule. To find the number of board feet in a piece of lumber, multiply il of the number of square inches in an end section of the piece by the number of feet in the length.

EXAMPLE 1. Find the number of board feet in a piece of lumber 1 foot wide, 2 inches thick, and 18 feet long. 2 x 12

x 18 = 36, the number of board feet in the piece. 12

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