Weight.—To determine weight, however, a scientific standard was adopted. A gallon contains 8.33 pounds avoirdupois weight of distilled water. This gallon is divided up in two ways; one by weight, and the other by measurement.
Each gallon contains 231 cubic inches of distilled water. As it has four quarts, each quart has 57 3/4 cubic inches, and as each quart is comprised of two pints, each pint has nearly 29 cubic inches.
The Gallon.—The legal gallon in the United States is equal to a cylindrical measure 7 inches in diameter and 6 inches deep.
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 dol[p. 145]lar, 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 latitude 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.