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was agreed upon in 1883 by the principal railroad companies of the United States and Canada. By this system, time meridians 15° apart have been established. The United States uses the meridians 75°, 90°, 105°, and 120° west from Greenwich. Places within the belt extending 71° east or west of a time meridian have the time of the time meridian. Therefore, the time between two places differs by whole hours, or not at all. The belts are named, beginning with the 75th meridian, as follows: Eastern Time, Central Time, Mountain Time, and Pacific Time.
227. Irregularities.-While the time meridians are exactly 15° apart, the belts using the several meridian times vary to suit the convenience of the railroads. This causes great irregularities. El Paso, Texas, has the same standard time as Savannah, yet there is a difference of 1 hr. 41 min. 30 sec. in local time. On the other hand, San Diego, California, has two hours later standard time than El Paso, although there is a difference of only 42 min. in local time.
1. The longitude of Buffalo is about 79° W. When it is noon in that city by standard time, what is the sun-time?
2. If a man travels from San Francisco to St. Louis, what change should he make in his watch?
3. Washington, D. C., is in longitude about 77° W. When it is 6 o'clock p. m. in that city by sun-time, what is the hour by a clock keeping standard time?
4. A man living in Galveston, Texas, observed that his clock, correct by sun-time, was 19 min. slower than the depot clock, correct by standard time. Find the longitude of Galveston.
5. Explain how the following information could reach the United States on Sunday, Feb. 28, 1904:
For two hours yesterday morning [Monday, Feb. 29, 1904], the Japanese squadron bombarded Port Arthur, injuring the Askold and Novik, and again damaging the Retvisan. The Japanese fleet is reported to have escaped injury.-Harper's Weekly.
IX. MEASURES OF TEMPERATURE
228. Temperature is usually measured by a thermometer constructed upon one of the following scales:
(1) Fahrenheit (F.), boiling-point 212°, freezing-point 32°. (2) Centigrade (C.), boiling-point 100°, freezing-point 0°. (3) Réaumur (R.), boiling-point 80°, freezing-point 0°.
Boiling point F. of water + 212°
Freezing point of water
° C. 4° R.
54 × 5 C.
= 54 × 4° R.
EXAMPLES, WITH SOLUTIONS
1. +86° F. corresponds to what readings on C. and R.?
· 32° F. 54° F.
= num. of degrees above freezing.
(1) 86° F. (2) 1° F. (3) 54° F. (4) 54° F.
30° C. = 24° R.
(5) 54° F. +
32° F. 86° F.
.. 86° F. corresponds to 30° C. and 24° R.
5° " = 1°
NOTE.-Degrees above 0°
on each scale are usually indicated by the sign+; below, by the sign -.
2. -4° F. corresponds to what readings on C. and R.?
num. degrees below freezing.
(1) 4° F. (2) 1° F.
° C. = 4° R.
= 36 × 5° C.
20° C. =
36° F. =
(5) - 36° F. + 32° F. =
- 4° F. corresponds to
3. +24° R. corresponds to what readings on F. and C.?
= 100° C.
= 180° F.
- 10° C.
(1) 80° R.
= 86° F.
(5) 54° F. + 32° F.
20° C. and
36 × °R.
4. -10° C. corresponds to what readings on F. and R.?
· 180° F. = 80° R.
(4) - 10° C.
24 x 5° C.
1. C. reads 10° above zero; what are the readings of F. and R.?
2. The temperature of the room is 68° F. Find the temperature in C.; in R.
3. Lead melts at 335° C. 4. Silver melts at 1040° C. in F.
Find its melting point in F.
5. On a certain day the temperature fell from 95° F. to 10° C. How many degrees R. did it fall?
X. THE METRIC SYSTEM
229. The Metric System of weights and measures is used by all scientific writers throughout the civilized world. It is employed in the affairs of everyday life by most nations except the United States and Great Britain.
NOTE.-The Metric System was originated by the French. Two surveyors, Delambre and Méchain, measured an arc of the meridian from Dunkirk, France, to Barcelona, Spain (a distance of about 10 degrees). From this they computed the distance from the equator to the pole. The quadrant thus obtained was divided into ten million equal parts; one part was made the base of the system, and was called a meter. All measures are derived from the meter. The system was adopted by France in 1840, and legalized in the United States in 1868.
230. The meter (Greek metron, measure) is the unit of length, and is 39.37043 inches long.
The multiples and submultiples of the meter and of the units derived from it are based on the decimal scale.
The multiple units are designated by Greek prefixes They are: deka (10), hekto (100), kilo (1000), and myria (10000). The submultiple units are designated by Latin prefixes. They are: deci (.1), centi (.01), and milli (.001).
An abbreviation of a submultiple begins with a small letter, while an abbreviation of a multiple begins with a capital letter.
Many of the denominations given in the tables are not in common use. Those usually employed in business or science are printed in bold-faced type.
MEASURES OF EXTENSION
231. The unit is the meter, about 39.37 inches.
100 sq. meters
100 sq. dekameters
100 sq. hektometers
NOTE.-In measuring land, the square meter is called a centare (ca), the square dekameter an are (a), and the square hektometer a hektare (Ha).
1 sq. centimeter (sq. cm.).
1 sq. decimeter (sq. dm.).
1 sq. meter (sq. m.).
1 sq. dekameter (sq. Dm.).
1 sq. hektometer (sq. Hm.)
1 sq. kilometer (sq. Km.). 247.114 A .386 (sq. mi.).