Practical Mechanics for Boys Part 14

Notwithstanding the weights and dimensions of solids and liquids are thus fixed by following a scientific standard, the divisions into scruples, grains, pennyweights and tons, as well as cutting them up into pints, quarts and other units, is done without any system, and for this reason the need of a uniform method has been long considered by every country.

THE METRIC SYSTEM.--As early as 1528, Fernal, a French physician, suggested the metric system. Our own government recognized the value of this plan when it established the system of coinage.

The principle lies in fixing a unit, such as a dollar, or a pound, or a foot, and then making all divisions, or addition, in multiples of ten.

Thus, we have one mill; ten mills to make a dime; ten dimes to make a dollar, and so on.

BASIS OF MEASUREMENT.--The question arose, what to use as the basis of measurement, and it was proposed to use the earth itself, as the measure. For this purpose the meridian line running around the earth at the lat.i.tude of Paris was selected.

One-quarter of this measurement around the globe was found to be 393,707,900 inches, and this was divided into 10,000,000 parts. Each part, therefore, was a little over 39.37 inches in length, and this was called a meter, which means _measure_.

A decimeter is one-tenth of that, namely, 3.937 inches; and a decameter 39.37, or ten times the meter, and so on.

For convenience the metrical table is given, showing lengths in feet and inches, in which only three decimal points are used.

Metrical Table, showing measurements in feet and inches:

METRICAL TABLE, SHOWING MEASUREMENTS IN FEET AND INCHES

------------------------------------------ ------------+--------------+-------------- Length | Inches | Feet ------------+--------------+-------------- Millimeter | 0.039 | 0.003 Centimeter | 0.393 | 0.032 Decimeter | 3.937 | 0.328 Meter | 39.370 | 3.280 Decameter | 393.707 | 32.808 Hectometer | 3937.079 | 328.089 Kilometer | 39370.790 | 3280.899 Myriameter | 393707.900 | 32808.992 ------------+--------------+--------------

METRIC SYSTEM, SHOWING THE EQUIVALENTS IN OUR MEASURES

1 Myriameter = 5.4 nautical miles, or 6.21 statute miles.

1 Kilometer = 0.621 statute mile, or nearly 5/8 mile.

1 Hectometer = 109.4 yards.

1 Decameter = 0.497 chain, 1.988 rods.

1 Meter = 39.37 inches, or nearly 3 ft. 3-3/8 inches.

1 Decimeter = 3.937 inches.

1 Centimeter = 0.3937 inch.

1 Millimeter = 0.03937 inch.

1 Micron = 1/25400 inch.

1 Hectare = 2.471 acres.

1 Arc = 119.6 square yards.

1 Centaire, or square meter = 10.764 square feet.

1 Decastere = 13 cubic yards, or about 2-3/4 cords.

1 Stere, or cubic meter = 1.308 cubic yards, or 35.3 cubic feet.

1 Decistere = 3-1/2 cubic feet.

1 Kiloliter = 1 ton, 12 gal., 2 pints, 2 gills old wine measure.

1 Hectoliter = 22.01 Imperial gals., or 26.4 U. S. gals.

1 Decaliter = 2 gallons, 1 pint, 2-2/5 gills, imperial measure, or 2 gals., 2 qts., 1 pt., 1/2 gill, U. S.

1 Liter = 1 pint, 3 gills, imperial, or 1 qt., 1/2 gill U. S. measure.

1 Decileter = 0.704 gill, imperial, or 0.845 gill U. S. measure.

1 Millier = 2,204.6 pounds avoirdupois.

1 Metric quintal = 2 hundredweight, less 3-1/2 pounds, or 220 pounds, 7 ounces.

1 Kilogram = 2 pounds, 3 ounces, 4-3/8 drams avoirdupois.

1 Hectogram = 3 ounces, 8-3/8 drams avoirdupois.

1 Decagram = 154.32 grains Troy.

1 Gram = 15.432 grains.

1 Decigram = 1.542 grain.

1 Centigram = 0.154 grain.

1 Milligram = 0.015 grain.

CHAPTER XIII

USEFUL INFORMATION FOR THE WORKSHOP

To find the circ.u.mference of a circle: Multiply the diameter by 3.1416.

To find the diameter of a circle: Multiply the circle by .31831.

To find the area of a circle: Multiply the square of the diameter by .7854.

To find the area of a triangle: Multiply the base by one-half the perpendicular height.

To find the surface of a ball: Multiply the square of the diameter by 3.1416.