## Elements of Surveying |

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Page 15 - FRACTION is a negative number, and is one more than the number of ciphers between the decimal point and the first significant Jigure.

Page 55 - 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 25 - In any triangle, the sum of the two sides containing either angle, is to their difference, as the tangent of half the sum of the two other angles, to the tangent of half their difference.

Page 7 - NB 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 98 - The line so determined makes, with the true meridian, an angle equal to the azimuth of the pole star; and from this line the variation of the needle is readily determined, even without tracing the true meridian on the ground. Place the compass upon this line, turn the sights in the direction of It, and note the angle shown by the needle. Now, if the elongation at the time of observation...

Page 21 - The circumference of every circle is supposed to be divided into 360 equal parts called degrees, each degree into 60 equal parts called minutes, each minute into 60 equal parts called seconds.

Page 12 - ... from the right hand as many places for decimals as there are figures in the multiplier, and add the product, so obtained, to the first logarithm, for the logarithm sought.

Page 10 - The logarithm of any root of a number, is equal to the logarithm of that number divided by the index of the root.

Page 95 - But the star being at a distance from the pole equal to 1° 30' nearly. It performs a revolution about the pole in a circle, the polar distance of which is 1° 30': 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.

Page 34 - ... the square of the hypothenuse is equal to the sum of the squares of the other two sides.