For what purpose is Apothecaries' Weight used? Do its pound and ounce differ from Troy Weight?

AVOIRDUPOIS WEIGHT.

68. By this weight are weighed all things of a coarse or drossy nature, as bread, butter, cheese, flesh, groceries, and some liquids; all metals, except gold and silver.

The pound Avoirdupois contains 7000 grains.

From the preceding table, it will be seen that 112 pounds instead of 100, are called one hundred weight. In most cases however the hundred weight is taken equal to 100 pounds, and 25 pounds, instead of 28, is called a quarter. Coal merchants in buying coal receive 112 pounds for a hundred weight, and 20 hundred weight for a ton, making 2240 pounds; but they retail it at 2000 pounds for a ton.

What substances are weighed by Avoirdupois Weight? Repeat the Table. By this weight how many pounds make one hundred weight? In most cases how many pounds make a hundred weight? How is coal usually bought and sold?

LONG MEASURE.

69. It is usual, at the present time, to derive the measure of length from that of a pendulum vibrating once in a second of time. The length of such pendulums will vary for different latitudes, as here given.

The French government derive their linear unit of measure from one quarter of the circumference of a great circle of the earth passing through the poles. Having determined by actual surveys the length of that portion of such a circle comprised between the parallels of Dunkirk

and Barcelona, they deduced its entire length from the equator to the pole, and took one ten millionth part of it for a metre. This method gave for the French metre 39-37079 English inches, equal 3-2809 feet, nearly.

How do the French
What is its length

From what is the measure of length, at the present time, usually derived? Mention the lengths of the second's pendulum for the places given above. derive their measure of length? How is their metre obtained? in English inches? What is the length in feet? Repeat the Table of Long Measure.

* This measure has fallen into disuse, and for small portions of an inch, we use one-eighth, one-tenth, and one-sixteenth.

The latest measurements give the equatorial diameter of the earth equal to 7925-648 miles, and its circumference equal to 24899 miles, which, divided by 360, gives the length of a degree 694 miles, nearly. The circumference corresponding with the equator is nearly circular, while the circumference passing through the poles is elliptical.

71. This measure is used for estimating artificers' work, such as boards, glass, pavements, plastering, flooring, painting, and any other kind of work where length and breadth only are concerned. It is always employed for measuring land, and for this reason it is sometimes called Land Measure.

A square is a figure having four equal sides, and all its angles right, that is, the sides are perpendicular to each other.

If the length of one of the sides is one inch, it is called a square inch. If the length of one of the sides is one foot, or 12 inches, it is called a square foot, which by the adjacent figure we see is composed of 12×12=144 square inches.

In a similar manner, if we

1 foot-12 inches.

1 foot 12 inches.

had a square, each of whose sides was 3 feet, then it would contain 3 x3=9 Sq. feet, which is called one square yard, since 3 feet=1 yard.

TABLE.

144 square inches Sq. in. make 1 square foot, 9 square feet

Sq. ft.

66.

1 square yard,

Sq. yd.

In measuring land, Gunter's chain is used; its length is 4 rods, or 66 feet. It is divided into 100 links.

What use is made of Square Measure? When employed in measuring land, how is it called? What is a square? When a square is one inch on each side how is it called? When it is one foot or 12 inches on each side how is it called? When it is one yard on each side how is it called? Repeat the Table of Square Measure. In Land Measure, with what are the sides of the field usually measured? How long is this chain? Repeat the Table of Land Measure.

* The acre is in all cases applied to surface or area. There is no such thing as an acre long, or a cubic acre. It is of such a magnitude as not to admit of being accurately given in the form of a square, having the sides exactly determined. The same remarks are applicable to the rood.