Look now at the system. The metre, which is assumed to be one ten-millionth part of the distance from the equator to the pole, is, in fact, 39⅓ inches, or 39.37 inches, in length. It is especially the unit of length; but it is also the unit from which are derived all measures of weight and capacity, square or cubic. It is at once foundation-stone and cap-stone. It is foundation-stone to all in the ascending series, and cap-stone to all in the descending series.
The unit of surface measure, or land measure, is the are, from the Latin area, and is the square of ten metres, or, in other words, a square of which each side is ten metres in length.
The unit of solid measure is the stere, from the Greek, and is the cube of a metre, or, in other words, a solid mass one metre long, one metre broad, and one metre high.
The unit of liquid measure is the litre, from the Greek, and is the cube of the tenth part of the metre, which is the decimetre; or, in other words, it is a vessel where by interior measurement each side and the bottom are square decimetres.
The unit of weight is the gram, also derived from the Greek, and is the one-thousandth part of the weight of a cubic litre of distilled water at its greatest density,—this being just above the freezing-point.
Such are main elements of the metric system. But each of these has multiples and subdivisions. It is multiplied decimally upward, and divided decimally downward. The multiples are from the Greek. Thus, deca, ten, hecto, hundred, kilo, thousand, and myria, ten thousand, prefixed to metre, signify ten metres, one hundred metres, one thousand metres, and ten thousand metres. The subdivisions are from the Latin. Thus, deci, centi, milli, prefixed to metre, signify one tenth, one hundredth, and one thousandth of a metre. All this appears in the following table.
| Metric Denominations and Values. | Equivalents in Denominations in use. |
|---|---|
| Myriametre, 10,000 metres, | 6.2137 miles. |
| Kilometre, 1,000 metres, | .62137 mile, or 3,280 feet and 10 inches. |
| Hectometre, 100 metres, | 328 feet and 1 inch. |
| Decametre, 10 metres, | 393.7 inches. |
| Metre, 1 metre, | 39.37 inches. |
| Decimetre, ⅒ of a metre, | 3.937 inches. |
| Centimetre, ¹⁄₁₀₀ of a metre, | .3937 inch. |
| Millimetre, ¹⁄₁₀₀₀ of a metre, | .0394 inch. |
These same prefixes may be applied in ascending and descending scales to the are, the litre, and the gram. Thus, for example, we have in the ascending scale, decagram, hectogram, kilogram, and myriagram,—and in the descending scale, decigram, centigram, milligram.
In this brief space you behold the whole metric system of weights and measures. What a contrast to the anterior confusion! A boy at school can master the metric system in an afternoon. Months, if not years, are required to store away the perplexities, incongruities, and inconsistencies of the existing weights and measures, and then memory must often fail in reproducing them. The mystery of compound arithmetic is essential in the calculations they require. All this is done away by the decimal progression, so that the first four rules of arithmetic are ample for the pupil.