Elementary arithmetic, with brief notices of its history... by Robert Potts.

8

APOTIECARIES' LIQUID MEASURE.
60 minims are equal to 1 drani
8 drams,, 1 ounce
20 ounces,, 1 pint.
Tile liquid dram and ounce are the same as the Avoirdupois dram
and ounce.
TheY WEIGHT.
24 grains are equal to 1 pennyweight
20 pennyweights,, 1 ounce
12 ounces,, 1 pound.
Troy weight is used for gold and silver and precious stones.
English standard gold contains 22 parts pure gold and 2 parts
alloy, and is named by goldsmiths, gold of 22 carats fine. The price
of standard gold is fixed by law at ~3 17s. 10ld. an ounce, but the
Mint purchases gold at ~3 17s. 9d. an ounce, with certain small
allowances.
Standard silver consists of 37 parts pure silver and 3 parts alloy.
MEASURES OF LENGTH, SUrFACE, AND VOLUMIE.
6. There are three distinct kinds of magnitude, the line or length,
the surface or area, and the volume or solid. The line has one dimension, length only. The surface has two dimensions, length and breadth.
The solid has three dimensions, length, breadth, and thickness.
The unit of length is a straight line of definite and known length,
assumed as the primary unit of measure. Any length or distance is
measured by finding how many times the assumed unit of length is
contained in the distance to be measured. Units both of greater and
less magnitude have been contrived for the measurement of large
and small distances, and in general consist of some multiple or submultiple of the assumed primary unit of length.
The square is assumed for the measure of surfaces, and the unit
of area is assumed to be a square the side of which is a line one unit
in length. To measure a surface or area is to determine the number
of times it contains the square unit of area.
To shew that the number of square units in a rectangle or a rectangular
parallelogram is expressed by the product of the numbers of lineal units contained in the length and breadth of the rectangle.
Let the side AB of the rectangle AB CD contain 5 units and the
breadth AD) 4 units.'
The product 5 x 4 will denote the number of square units in the
area of the rectangle.

1 The student is recommended to draw the figures for himself. He may see,
the figures referred to in the notes cn Books II. and XI. of the Editor's Edition of
Euclid's Elements.