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KEY TO THE SCALE.
DESCRIPTION OF THE SCALE.
The figures on both parts of the scale, are precisely alike, and may be called whole numbers or parts of numbers, according to the nature of the problem to be solved. The large figure 1 may be called Tobo, or ndo, or it, or 1, or 10, or 100, or 1000, or 10000, &c., &c. If it be called tobo, the large figure 2 will be to go, the large 3 will be todo, and so on; and the next sized figures between those large ones, will then be rodovi to do, to do, &c.; and the still smaller ones will be tootoo, &c. If the large 1 be called 1, then 2 is 2, 3 is 3, &c.; and the next sized figures are tenths, and the third sized ones are hundredths, &c. If the large 1 be called 10, the large 2 is 20, 3 is 30, &c.; and the next sized figures are whole numbers—the first after the 1 is 11, the next 12, the next 13, &c. If the large I be called 100, 2 is 200, &c.; and the next sized figures then will read 10, 20, 30, &c.; and the smallest sized figures will then be whole numbers.
N. B.—Whenever fig. 1 is referred to, it means the large fig. 1 at the diamond--unless otherwise explained.
A TABLE OF GAUGE POINTS USED ON
I., at the diamond, is the gauge point for Multipli sation, Division, &c., &c.
A. Area of a Circle.
for months, at 7 per cent. 2. for months, at 6
cent. for days, at 8 per cent. for days, at 7 per cent.
for days, at 6 per cent. 107. Compound Int. for years, at 7 per cent. 106. do. do. do. 6 do. 160. for Acres. 144. for Square Timber. 9. Yds. Square. 886. Square and Circle, equal in Area. 707. Inscribed Square. 577. side of Inscribed Cube.
87. side of Inscribed Triangle. 589. side of Pentagon, (5 sides.) 5. side of Hexagon, (6 sides.) 437. side of Heptagon, (7 sides.) 383. side of Octagon, (8 sides.) 337. side of Nonagon, (9 sides.) 31. side of Decagon, (10 sides.) 282. side of Undecagon, (11 sides ) 26. side of Dodecagon, (12 sides.) 464. diameter of 3 Inscribed Circles. 416. diameter of 4 Inscribed Circles. 785 · point for Area. 314 . point for Circumference.
To PERFORM MULTIPLICATION.
RULE.–First find the multiplier on the circular. Place it opposite 1, then opposite the multiplicand found on the fixed part, is the product on the circular.
Example.—What is the product of 4 by 2 ?
Place 2 opposite 1: then opposite 4 is the product -8.
N. B.-Observe, now, that all the numbers and parts of numbers on the fixed part, are multiplied by 2, and their products are directly opposite them on the circular. So of any other multiplier.
What is the product of 12 by 7?
Of 3 by 3?
What is the product of 8 by 21 ?
What is the product of 10 by 5 ?
have to use the same figures both