60 
POPULAE SCIENCE EEVIEW. 
double and its balf^ as by law established. We give in a table 
the corresponding units of volume and weight : — 
Meter cube ... Kiloliter 
Decimeter cube ... Liter 
Centuneter cube . . . INIilliliter 
jMillimeter cube ... 
Metric ton (1000 kilogs.). 
Kilogram (1000 grams). 
Gram 
Milligram. 
We perceive that each series constitutes a decreasing geome- 
tric progression^ the ratio of which toVo- The cubes of the 
meter^ decimeter^ and centimeter, filled with distilled water, 
are equivalent in weight to the metric ton, kilogram, and gram 
respectively, and the relation established between volume and 
weight is of great importance in the mechanical arts and in 
trade. The specific gravity of a body, whether solid or fluid, 
as we know, is the relation or ratio of the weight of any 
volume of this body to the ■weight of an equal volume of water. 
Now, as we have a series of volumes and weights correspond- 
ing in the metric scale, expressed in single units, the investi- 
gation of the specific gravity of bodies, this being a constant 
quantity in each, is proportionally simplified. Assuming as 
unit of volume the decimeter cube, or liter, and as unit of 
weight the kilogram, as is the ordinary practice in the arts in 
France, then the specific gravity of a body is the w^eight in 
kilograms of a decimeter cube of this body. This simple 
process furnishes also an easy method of ascertaining the 
weight, and therefore ‘value, of merchandise of large bulk ; for 
the cubic dimensions of this bulk being found by direct measure- 
ment, as can be done by the metric scale better and more 
accurately than by any other, this volume, multiplied by the 
specific gravity of the substance, gives the weight of the mer- 
chandise in kilograms. In delicate measurement, such as in 
pharmacy and chemical analysis, the gram (along with its sub- 
divisions) and its concomitant unit of volume, the cubic centi- 
meter, are used. And in shipping, the metric ton and its 
corresponding unit of volume, the cubic meter, furnish the 
utmost advantage and facility in estimating either the tonnage 
or the cargo of the ship. 
It is almost superfluous to contrast the unity and harmony 
of this unique system called Metric with our own grotesque 
scales of weights and measures. In the former, all the parts 
are subordinate to the meter, the primary unit; they all emanate 
from it, and radiate as from a common centre. Our standards, 
on the contrary, are not only arbitrary, but unconnected one 
with another; there is, moreover, no fixity about them, but 
like so many independent variables, they pass through difierent 
series of values from maximum to minimum, with the utmost 
caprice and nonchalance. We learn from Kelly^s Universal 
