c., and the only other denomination of volume we shall have
occasion to use is the "litre," which measures 1000 c.c., and is roughly
1-3/4 pints.
The weights used are kept in boxes in a definite order, so that the
weights on the balance can be counted as well by noting those which are
absent from the box as by counting those present on the scale-pan. The
weights run 50, 20, 10, 10, 5, 2, 1, 1 and 1 grams, and are formed of
brass. The fractions of the gram are generally made of platinum or of
aluminium, and are arranged in the following order:--0.5, 0.2, 0.1, 0.1,
and 0.05, 0.02, 0.01, 0.01. These may be marked in this way, or they may
be marked 500, 200, 100, 100, 50, 20, 10, 10; the 500 meaning 500
milligrams.
Some makers send out weights in the series 50, 20, 20, 10, &c.
Weights of less than 0.01 gram are generally present in a box, but it is
much more convenient to work with a rider. This is a piece of wire which
in the pan weighs 0.01 gram; it is made in such a form that it will ride
on the beam, and its effective weight decreases as it approaches the
centre. If the arm of the beam is divided into tenths, then each tenth
counting from the centre outward equals 0.001 gram or 1 milligram, and
if these tenths be further subdivided the fractions of a milligram are
obtained; and these give figures in the fourth place of decimals.
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