Centigramme 0.01 or

=

Milligramme = 0.001 or Tooth

All the terms of this latter, or divisional series are found useful; but only the kilogramme, in addition to the unit itself, is found requisite for ordinary use in the multiple series. The kilogramme, or thousand-gramme-weight, is the weight of the cube which results from dividing the metre cube into a thousand equal parts in other words, from dividing the edge of the metre cube (i. e. the metre) into 10 parts (i. e. 10 decimetres) and cubing one of these parts (so as to obtain the decimetre cube). This same decimetre cube is also adopted as the unit for measures of capacity, in which function it loses the name kilogramme, and receives instead the appellation litre (from the term Airpa, in use among the Greeks for the designation of one of their standards of quantity). From this unit of capacity, as the starting-point, the following capacity-measures are obtained by decimal multiplication and division, distinguished by Greek and Latin prefixes, as before :—

All the measures in this table are employed alike for wet and dry bodies (wine, grain, &c.), and they are all more or less in

FRENCH CUBIC MEASURE.

129

use. The highest term (the kilolitre) corresponds to the metre cube, the unit of solid measure. The lowest degree of the table, or millilitre, is identical with the centimetre cube (i. e. the millionth of the metre cube, the die-like mass which, in distilled water, represents one gramme), and it is under this name that it is most commonly used.

It only remains to set forth the metrical cubic measures, which start, like the linear measures, from the metre cube, and form the two following series:

The cubic metre is in common use as a measure of wood used for fuel; in which capacity it takes the appellation stere, from the Greek σTEρεóc, solid. From this, as from the other units of measure, a multiple and divisional series may be derived by aid of the Greek and Latin prefixes; but of the series so formed only one member, the decistere, or tenth of a stere, has proved needful, and come into use.

The highest term in each of the multiple series we have tabulated is that with the prefix kilo. This may, however, in each case, be decupled by substituting for kilo the prefix myria (also Greek). Thus a myriametre is equal to ten kilometres; a myrialitre to ten kilolitres, and so forth. These high expres

G 3

130

OUMFALISON OF FRENCH AND ENGLISH METRICAL UNITS.

sions, however, are comparatively seldom required; and we have kept our tables simpler by reserving this, their final term, for separate mention, once for all, here at the close of our description.

It only remains to bring the units of this philosophical metric system into comparison with those of the English arbitrary scheme (the expression system would here be inappropriate) in order simultaneously to display, first, the marked superiority of the French over the English system; secondly, the arithmetical data for transforming the denominations of each into the other; and thirily, the unwelcome amount of gratuitous toil attending such elaborate reductions. In the following table the French metrical units are placed in regard with, and reduced into terms of, their respective English correlatives :—

For our present purposes attention should be particularly directed, first, to the units of weight and volume, namely, the gramme and the litre, in terms of which the weight and volume ratios with which we have to deal are best expressed; and, secondly, on the unit of length, the metre, in terms of which the barometric pressure is best expressed, the average height of the mercurial column being 0.76 metre = 76 centimetres = 29.9218 English inches.

Closing here our parenthetical account of the metrical system, and reverting to our immediate subject, we have now to select an appropriate volume, with its corresponding weight, to serve as our standard unit of measurement.