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THEORY AND PRACTICE

OF

SURVEYING.

1040

THE

HE word Surveying, in the Mathematics, signifies the art of measuring land, and of delineating its boundaries on a map.

The Surveyor, in the practice of this art, directs his attention, at first, to the tracing and measuring of lines; secondly, to the position of these lines in respect to each other, or the angles formed by them; thirdly, to the plan, or representation of the field, or tract, which he surveys; and fourthly, to the calculation of its area, or superficial content. When this art is employed in observing and delineating Coasts and Harbours, in determining their variation of the Compass, their Latitude, Longitude and soundings, together with the bearings of their most remarkable places from each other, it is usually denominated Maritime-Surveying. This branch of Surveying, however, demands no other qualifications than those, which should be thoroughly acquired by every Land Surveyor, who aspires to the character of an accomplished and skilful practitioner. Surveying, therefore, requires an intimate acquaintance with the several parts of the Mathematics, which are here inserted as an introduction to this trea

tise.

B

PART I.

Containing Decimal Fractions, Involution and Evo

lution, the Nature and Use of Logarithms, Geometry and Plane Trigonometry.

SECTION I.

DECIMAL FRACTIONS.

a

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If we suppose unity or any one thing to be divided into any assigned number of equal parts, this number is called the denominator; and if we chuse to take any number of such parts less than the whole, this is called the numerator of a fraction.

The numerator, in the vulgar form, is always written over the denominator, and these are separated by a small line thus , or s; the first of these is called three-fourths, and the latter five-eighths of an inch, yard, &c. or of whatever the whole thing originally consisted: the 4 and the 8 are the denominators, showing into how many equal parts the unit is divided; and the three and the five are the numerators, showing how many of those parts are under consideration,

Fractions are expressed in two forms, that is, either vulgarly or decimally.

All fractions whose denominators do not consist of a cipher, or ciphers, set after unity, are called vulgar; and their denominators are always written under their numerators. The treatment of these, however, would be foreign to our present purpose. But fractions whose denominators consist of an unit prefixed to one or more ciphers, are called decimal fractions; the numerators of which are written without their denominators, and are distinguished from integers by a point

a prefixed: thus to, top and 100, in the decimal form, are expressed by .2.42 .172.

172

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1000

The denominators of such fractions consisting always of an unit, prefixed to as many ciphers as there are places of figures in the numerators, it follows, that any number of phers put after those numerators, will neither increase nor lessen their value: for, and are all of the same value, and will stand in the decimal form thus .3 .30 .300; but a cipher, or ciphers prefixed to those numerators lessen their value in a tenfold proportion: for % and 10%, which in the decimal form we denote by .3 .03. and .003, are fractions, of which the first is ten times greater than the second; and the second, ten times greater than the third.

CTIONS.

one thing to be of equal part or; and if we chose

parts less than the

rator of a fraction

ar form, is always

nd these are sepa the first of thes latter five-s atever the h

and the 8 are the

any equal parts and the fire re of those parts

forms, that is

lo not consist ity, are cal

are always

e treatment

to our pre nominators re ciphers, nerators of

Ominators,

Dy a point decimal

Hence it appears, that as the value and denomination of any figure, or number of figures, in common arithmetic is enlarged, and becomes ten, or an hundred, or a thousand times greater, by placing one, or two, or three ciphers after it; so in decimal arithmetic, the value of any figure, or number of figures, decreases, and becomes ten, or a hundred, or a thousand times less, while the denomination of it increases, and becomes so many times greater, by prefixing one, or two, or three Giphers to it and that any number of ciphers, before an integer, or after a decimal fraction, has no effect in changing their values.

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Add 62 121.306.75 27 and 9007 to gether. 121-06

.75 2.7 .0007

Sum=130.9567

What is the sum of 6.57 1.026.75 1455 8.7 526. 3.97 and .0271?

Answer 6935131.

What is the sum of 451 146.071 507 .0006 132. 62.71 507 7.9 and .10712?

Answer 351.31972.

SUBTRACTION OF DECIMALS. Write the figures of the subtrahend beneath those of the minuend according to the denom nation of their places, as directed in the rule of addition; then, beginning at the right hand, subtract as in whole numbers, and place the decimal point in the difference exactly under the other two points.

EXAMPLES
From 38.765 take 35.3741

25.3741

Difference=13.3909.

From 2.4 take .8472

.8472

Diff. = 1.5528

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