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

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A.S. Barnes & Company, 1852 - Navigation - 392 pages

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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 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 was 33 45' ; required the height of the tower.
Page 1 - O's, to catch the eye, and to indicate that from thence the two figures of the Logarithm to be taken from the second column, stand in the next line below. N. Log. N. Log. N. Log. N. Log. 1 2 3 4 5 o.
Page 21 - ... 20. An EQUILATERAL polygon is one which has all its sides equal ; an equiangular polygon, is one which has all . its angles equal. 21. Two polygons are mutually equilateral, when they have their sides equal each to each, and placed in the same order : that is to say, when following their...
Page 113 - Longitude of the preceding course^ plus the Departure of that course, plus the Departure of the course itself* The Double Longitude of the last course (as well as of the first) is equal to its Departure. Its "coming out" so, when obtained by the above rule, proves the accuracy of the calculation of all the preceding Double Longitudes.
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 17 - The minutes in the left-hand column of each page, increasing downwards, belong to the degrees at the top ; and those increasing upwards, in the right.hand column, belong to the degrees below.
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 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...

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