# Elements of Surveying, and Navigation: With Descriptions of the Instruments and the Necessary Tables

A.S. Barnes, 1857 - Navigation - 393 pages
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### Contents

 Of Logarithms 9 Multiplication by Logarithms 15 Definitions 19 Geometrical Constructions 25 Gunters Scale 32 SECTION III 38 Theorems 44 Solution of RightAngled Triangles 54
 Of Supplying Omissions in the Field Notes 124 SECTION IV 131 Method of Ascertaining the Variations 138 The Y Level 147 Levelling in the Field 153 SECTION II 159 Field Notes 166 GEODESIC TRIGONOMETRIC AND MARITIME 172

 PLANE SURVEYING 64 Verniers 75 Surveying Cross 81 Of Laying out Land 96 Surveying with the Compass Definitions etc 102 Of Balancing the Work 109 First Method of Plotting 117
 Triangulation 178 To Measure a Horizontal Angle 185 Plotting the Triangulation 192 SECTION 1 201 SECTION III 207 SECTION V 214 Mercators Chart 221

### Popular passages

Page 10 - The logarithm of . the quotient of two numbers, is equal to the logarithm of the dividend diminished by the logarithm of the divisor.
Page 38 - The circumference of every circle is supposed to be divided into 360 equal parts, called degrees...
Page 45 - C' (89) (90) (91) (92) (93) 112. In any plane triangle, the sum of any two sides is to their difference as the tangent of half the sum of the opposite angles is to the tangent of half their difference.
Page 138 - ... the time of revolution is 23 h. and 56 min. To the eye of an observer, this star is continually in motion, 'and is due north but twice in 23 h. 56 min. ; and is then said to be on the meridian. Now, when it departs from the meridian, it apparently moves east or west, for 5 h. and 59 min., and then returns to the meridian again. When at its greatest distance from the meridian, east or west, it is said to be at its greatest eastern or western elongation.
Page 61 - Being on a horizontal plane, and wanting to ascertain the height of a tower, standing on the top of an inaccessible hill, there were measured, the angle of elevation of the top of the hill 40°, and of the top of the tower 51° ; then measuring in a direct line 180 feet farther from the hill, the angle of elevation of the top of the tower Cway 33° 45' ; required the height of the tower.
Page 9 - THE LOGARITHM: of a number is the exponent of the power to which it is necessary to raise a fixed number, to produce the given number.
Page 142 - Now, if the elongation, at the time of observation, was west, and the north end of the needle is on the west side of the line, the azimuth, plus the angle shown by the needle, is the true variation. But should the north end of the needle be found on the east side of the line, the elongation being west, the difference between the azimuth and the angle would show the variation, and the reverse when the elongation is east. 1. Elongation west, azimuth 2° 04' North end of the needle on the west, angle...
Page 39 - The secant of an arc is the line drawn from the centre of the circle through one extremity of the arc, and limited by the tangent passing through the other extremity. Thus, 00 is the secant of the arc AB.
Page 44 - CB : CA : : sin A : sin B. For, with A as a centre, and AD equal to the less side...
Page 22 - In a Right-angled Triangle, the side opposite the right angle is called the Hypothenuse ; and the other two sides are called the Legs, and sometimes the Base and Perpendicular.