Elementary text book for young surveyors and levellers

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Simpkin, Marshall & Company, 1856 - 185 sider

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Side 111 - All the interior angles of any rectilineal figure, together with four right angles, are equal to twice as many right angles as the figure has sides.
Side 160 - LEVELLING is the art of representing the inequalities of the earth's surface, and of determining the relative heights of any number of points above or below a line, equidistant, at every point, from the centre of the earth.
Side 17 - The square of the hypothenuse is equal to the sum of the squares of the other two sides ; as, 5033 402+302.
Side 8 - To describe a square upon a given straight line. Let AB be the given straight line : it is required to describe a square upon AB.
Side 102 - The existence of parallax is determined by moving the eye about, when looking through the telescope, observing whether the cross wires change their position, and are flittering and undefined. To correct this error, first adjust the eye-piece, by means of the moveable eye-piece tube, till you can perceive the cross wire clearly defined, and sharply marked against any white object.
Side 23 - C will be found 9, the square root on D. For the square root of 144 : Set 1 on C to 10 on D ; then against 144 on C will be found the square root 12 on D. 42. To find the area of a board or plank : The rule is, to multiply the length by the breadth, the product will be the area ; therefore, by the sliding rule, Set 12 on B against the breadth in inches on A ; then...
Side 16 - E, the adjacent angles CEA, AED; these angles are together equal to two right angles. (i. 13.) Again, because the straight line DE makes with AB...
Side 28 - To find the area of a circle. Rule — Multiply the square of the diameter by .7854; or the square of the radius by 3.1416; or the square of the circumference by .07958. Find the area of a piston 20 in. in diam. Answer— 20!
Side 8 - To draw a straight line at right angles to a given straight line, from a given point in the same. Let AB be the given straight line, and C the given point in it : it is required to draw from the point C a straight line at right angles to AB.
Side 23 - To find the Area of a Triangle when the Three Sides are given. Rule. — From half the sum of the three sides subtract each side separately. Multiply the half sum and the three remainders together, and extract the square root of the product.

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