18. How many cubic inches of water will the 2 doz. cans (Ex. 17) contain? 19. What will it cost to dig a cellar 36 ft. long, 24 ft. wide, and 6 ft. deep, at 20 cts. a cubic yard? WOOD MEASURE. 246. A pile of wood 8 feet long, 4 feet wide, and 4 feet high makes a Cord. One of the 8 feet in length of a cord of wood is a Cord Foot. NOTE. equal size. This may be illustrated by placing side by side 8 books of How many cords of wood in the following: 5. What is the cost of a pile of wood 10 ft. long, 4 ft. wide, and 8 ft. high, at $4 a cord? 6. How high must a pile of 4-foot wood be piled to contain 10 cords, if the pile is 50 ft. long? 7. How many cords of wood can be piled in a shed 24 ft. long, 18 ft. wide, and 12 ft. high? 8. How many cords of building-stone in a pile 18 ft. long, 6 ft. wide, and 3 ft. high? 9. At $3.50 a cord, what will be the cost of a pile of stone 15 ft. long, 41 ft. wide, and 5 ft. high? 10. How many cubic feet in a cord of 2-foot wood? 3-foot wood? 18-inch wood? CAPACITY OF BINS. 247. 1. A bushel fills 2150.42 cubic inches of space. How many bushels of wheat can be contained in a bin 5 ft. x 5 ft. x 4 ft. ? NOTE. 5 x 5 x 4 x 1728 ÷ 2150.42. A bushel fills 1 cu. ft. of space nearly. 2. A wine gallon fills 231 cubic inches of space. How many gallons of water can be contained in a rectangular tank 10 ft. by 8 ft. by 4 ft.? NOTE. A cubic foot of space contains 1728 gal. = 7} gal. nearly. Find the contents in bushels: 3. Of a bin 6 ft. long, 5 ft. wide, and 4 ft. high. 4. Of a wagon-box 10 ft. long, 42 in. wide, and 22 in. high. 5. Of a box 3 ft. by 21 ft. by 21 ft. 6. How high must a bin 8 ft. long and 5 ft. wide be built to contain 120 bushels? Find the contents in gallons: 7. Of a tank 8 ft. by 6 ft. by 21 ft. 8. Of a cistern 6 ft. by 5 ft. by 41 ft. 9. Of a tank 5 ft. square and 6 ft deep. 10. How many barrels of water will a cistern contain that is 6 ft. by 6 ft. by 7 ft.? 11. A circular cistern is 5 ft. in diameter and 6 ft. deep. How many barrels of water will it hold? 12. How deep must I build a bin that is 6 ft. square, to hold 90 bushels of wheat? 13. How deep must I build a tank that is 5 ft. square to hold 40 barrels ? LONGITUDE AND TIME. 248. A Meridian is an imaginary line running from the north pole to the south pole. All places on a meridian have the same time. NOTE. The meridians of Greenwich and Washington are the meridians that run through Greenwich and Washington. 249. Longitude is distance east or west from some standard meridian, as Greenwich or Washington. When two places are on the same side of the standard meridian, their difference in longitude is found by subtraction. When on opposite sides, their difference in longitude is found by addition. 1. What is the difference in longitude between two cities, one of which is 20° west longitude, the other 30° east longitude? 20° +30° 50°. Ans. = 2. What is the difference in longitude between two places, one of which is 40° E., the other 70° E.? NOTE. No two places can have a difference in longitude exceeding 180°. If, in finding difference in longitude by addition, the sum exceeds 180°, subtract the sum from 360° to find the true difference. The earth turns upon its axis from west to east once in 24 hours, thus of its entire circumference, or 15° of longitude, passes under the sun in 1 hour. Since the earth turns at the rate of 15° every hour, in 1 minute it turns of 15°, or 15', and in 1 second of 15', The earth rotates 15° in 1 hour, 15' in 1 minute, and 15" in 1 second. 3. The difference in longitude between two cities is 18° What is the difference in time? 30'. 30' 15| 18° SOLUTION. Since the earth turns 15° in 1 hr., 15' in 1 min., 15" in 1 sec., the time can be found by dividing the number of degrees, minutes, and seconds by 15. 4. The difference in time between two cities is 54 min, What is their difference in longitude? 19 sec. DIAGRAM SHOWING THE DIFFERENCE IN TIME AT DIFFERENT MERIDIANS. STANDARD OR RAILROAD TIME. 185 Let the figure on page 184 represent the earth rotating on its axis. When it is 6 P.M., November 22, on the prime meridian, it is noon of the same day at 90° west longitude, and midnight at 90° east longitude. It is therefore A.M. above 90° west longitude and P.M. below. How do we know where it is P.M. and where A.M. at a given place on the earth's surface? How long does it take a given point on the earth's surface to move once around its circle ? Through how many degrees does the earth rotate in one hour? In one minute? In one second? The student will notice that in travelling around the earth from west to east there is an apparent gain of one day, since in this case the traveller is going with the sun; in going around from east to west there is an apparent loss of one day. From the above considerations we see that there must be somewhere a line at which November 23, and in general each new day, must begin on the earth. This line is taken 180° from the prime meridian, and is called the date line. On crossing this line, ships either gain or lose a day, and must correct their calendar accordingly. Is it possible to have a day last 48 hours? Which way is the ship sailing if such is the case? If a person were to travel around the earth from east to west in 120 days, reckoning by local time in various places, in how many days would he actually make the trip? STANDARD OR RAILROAD TIME. 250. The railroad companies have divided the country into four time belts, extending north and south. All places in each belt take the time of the meridian which passes |