TABLE.* 24 grains gr. make 1 pennyweight, pwt. 02. 66 1 pound, lb. 12 ounces gr. pwt. 24- 1 02. 480= 20 = 1 lb. 5760-240-12=1 What was the original of all weights used in England? How was the grain ob tained? Is it still used as a weight? What substances are weighed by Troy weight Repeat the Table. APOTHECARIES' WEIGHT. 67. This weight, as its name would imply, is used in weighing medicines in small quantities, as for prescriptions. But drugs and medicines in gross are bought and sold by Avoirdupois Weight. The pound and ounce Apothecaries' Weight are the same as in Troy Weight. This scale of weights is said to have been borrowed originally from Troyes in France-bence its name. Some, however, contend that the name has reference to the monkish title given to London, of Troy Novant. 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 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 69 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. |