Chapter XXXV: Appendix: D

THE METRIC SYSTEM OF WEIGHTS AND MEASURES.

The initial unit of the Metric System is the Metre or unit of length, which represents one ten millionth part of the earth’s quadrant, or one forty-millionth part of the circumference of the earth around the poles. The multiples and sub-divisions of this and all the other units are obtained by the use of decimals, and for this reason the system is also known as the _decimal system_. The multiples are designated by the Greek prefixes, _deca_ = 10; _hecto_ = 100; _kilo_ = 1000; _myria_ = 10,000. For the sub-divisions Latin prefixes are employed, as follows: _deci_ = 1/10; _centi_ = 1/100; _milli_ = 1/1000. Thus for measures of length we have the following expressions, showing the abbreviations commonly employed, and the equivalents in the ordinary English standards of measurement--

1 Myriametre, Mm. = 10,000.0 M. = 6.2137 miles.
1 Kilometre, Km. = 1,000.0 M. = 0.6213 mile.
1 Hectometre, Hm. = 100.0 M. = 109.362 yards.
1 Decametre, Dm. = 10.0 M. = 32.8086 feet.
1 Metre, M. = 1.0 M. = 39.3704 inches.
1 Decimetre, dm. = 0.1 M. = 3.9370 "
1 Centimetre, cm. = 0.01 M. = 0.3937 "
1 Millimetre, mm. = 0.001 M. = 0.0393 "

From the unit of linear measure of metre is derived the unit of the measure of capacity or LITRE. This represents the cube of one-tenth part of a metre, or a cubic decimetre, and its multiples and sub-divisions with their corresponding equivalents in Imperial fluid measure are as follows:--

1 Myrialitre, Ml. = 10,000.0 L. = 2200.9667 imperial gallons.[91]
1 Kilolitre, Kl. = 1,000.0 " = 220.0966 " "
1 Hectolitre Hl. = 100.0 " = 22.0096 " "
1 Decalitre, Dl. = 10.0 " = 2.2009 " "
1 Litre, L. = 1.0 " = 35.2154 fluid ounces imperial.
1 Decilitre, dl. = 0.1 " = 3.5215 " " "
1 Centilitre, cl. = 0.01 " = 0.3521 " " "
1 Millilitre, ml. = 0.001 " = 0.0352 " " "
or
1 Cubic Centimetre, ccm. = 0.001 L. = 0.0352 " " "

The unit of weight in the metric system is the GRAMME. This is also derived from the metre, and represents the weight of one cubic centimetre, of water, or the quantity of distilled water, at its maximum density, 4° C. (39·2° F.), which would fill the cube of one-hundredth part of a metre. The relative value of the gramme, together with its multiples and sub-divisions, as compared with the English standards of weight, may be seen from the following table:--

1 Myriagramme, Mg. = 10,000.0 Gm. = 22.0461 pounds.
1 Kilogramme, Kg. = 1,000.0 " = 2.2046 "
1 Hectogramme, Hg. = 100.0 " = 3.5273 ounces avoir.
1 Decagramme, Dg. = 10.0 " = 154.3235 grains.
1 Gramme, Gm. = 1.0 " = 15.4323 "
1 Decigramme, dg. = 0.1 " = 1.5432 "
1 Centigramme, cg. = 0.01 " = 0.1543 "
1 Milligramme, mg. = 0.001 " = 0.0154 "

The expression _micro-millimetre_ is used for microscopic measurements, and denotes the thousandth part of a millimetre. Of the measures of capacity, the terms most commonly employed are the litre and the cubic centimetre. Thus a decalitre may also be expressed as 10 litres, a centilitre as 10 cubic centimetres, etc. Of the metric weights the gramme and its fractional parts, with their respective prefixes, are much used in analytical work. The kilogramme is largely employed in commercial transactions, and is commonly abbreviated _kilo_.

As a comparison of the values of some of the more frequently employed expressions of the metric and English systems, the following may be found convenient for reference:--

1 mm. (millimetre) = 1/25 of an inch.
1 cm. (centimetre) = 2/5 of an inch.
1 inch = 25 millimetres or 2-1/2 centimetres.
1 mg. (milligramme) = 0.01543 grain (or approx. 1/64 grain).
1 gm. (gramme) = 15.4324 grains.
1 Kg. (“Kilo” or kilogramme) = 2 lbs. 3-1/4 ozs. av.
1 pound avoir. = 453,592 grammes.
1 ounce avoir. = 28,350 grammes.
1 grain = 0.06479 gramme or 64.79 milligrammes.
1 cc. (cubic centimetre) = 16.9 minims Imperial measure.
1 L. (litre) = 35.21 fluid ounces Imperial measure, or 33.815 fluid
ounces Wine measure.
1 fluid ounce Imperial measure = 28.350 grammes.
1 pint Imperial measure = 567.0 grammes.
1 gallon Imperial measure = 4.536 litres, or 10 lbs. avoir. of pure water
at 62° F. and under an atmospheric pressure of 30 inches of mercury.

It may be well to bear in mind that on the Continent liquids are always weighed, not measured.