Elements of Surveying: With the Necessary TablesJ. & J. Harper, 1830 - 306 páginas |
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Página 42
... levels attached to the vernier plate , at right angles to each other , by small ... level , rests on the upper plane of the vernier plate , to which it is made ... difference between the to be divided into one hundred equal parts ...
... levels attached to the vernier plate , at right angles to each other , by small ... level , rests on the upper plane of the vernier plate , to which it is made ... difference between the to be divided into one hundred equal parts ...
Página 51
... difference of these two readings will be the true angle , unless the vernier ... level , is truly horizontal . If the instrument be accurately constructed ... level be truly horizontal . If not , direct the telescope to a distant and ...
... difference of these two readings will be the true angle , unless the vernier ... level , is truly horizontal . If the instrument be accurately constructed ... level be truly horizontal . If not , direct the telescope to a distant and ...
Página 71
... level the table ; after which , place the fiducial edge of the ruler against the small pin at the centre , direct it ... difference of the readings is the angle sought ; but , OF THE PLAIN TABLE .
... level the table ; after which , place the fiducial edge of the ruler against the small pin at the centre , direct it ... difference of the readings is the angle sought ; but , OF THE PLAIN TABLE .
Página 121
... level . Intersected , however , as it is , by valleys and ridges of mountains , it becomes an important problem to ascertain the difference between the distances of given points from the centre of the earth ; such difference is called ...
... level . Intersected , however , as it is , by valleys and ridges of mountains , it becomes an important problem to ascertain the difference between the distances of given points from the centre of the earth ; such difference is called ...
Página 122
... levels of those points . But AB = BE ( BE + 2EC ) , and AD- = DF ( DF + 2FC ) ( 228 ) * . In the common operations of levelling , the arcs AE , AF , are small ; and since the difference between small arcs and their tangents is very ...
... levels of those points . But AB = BE ( BE + 2EC ) , and AD- = DF ( DF + 2FC ) ( 228 ) * . In the common operations of levelling , the arcs AE , AF , are small ; and since the difference between small arcs and their tangents is very ...
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Página 57 - 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.
Página 15 - FRACTION is a negative number, and is one more than the number of ciphers between the decimal point and the first significant Jigure.
Página 15 - The characteristic of a number less than 1 is found by subtracting from 9 the number of ciphers between the decimal point and the first significant digit, and writing — 10 after the result.
Página 102 - 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...
Página 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.
Página 97 - 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.
Página 100 - ... three inches square, be nailed to the lower edge of it, for the purpose of holding a candle. About twenty-five minutes before the time of the greatest eastern or western elongation of the pole-star, as shown by the tables of elongations, let the theodolite be placed at a convenient point and leveled. Let the board be placed about one foot in front of the theodolite, a lamp or candle placed on the shelf at its lower edge; and let the board be slipped up or down, until the pole-star can be seen...
Página 2 - An Act for the Encouragement of Learning, by securing the copies of Maps, Charts, and Books, to the authors and proprietors of such copies during the time* therein mentioned," and extending the benefits thereof to the arts of designing, engraving, and etching historical and other prints.
Página 100 - Let the board be placed about one foot in front of the theodolite, a lamp or candle placed on the shelf at its lower edge ; and let the board be slipped up or down, until the pole-star can be seen through the hole. The light reflected from the paper will show the cross hairs in the telescope of the theodolite. Then, let the vertical spider's line be brought exactly upon the pole-star, and, if it is an eastern elongation that is to be observed, and the star has not yet reached the most easterly point,...
Página 100 - ... to coincide with the vertical hair. Then mark the point directly under the theodolite; the line passing through this point and the staff makes an angle with the true meridian equal to the azimuth of the pole-star. From the table of azimuths, take the azimuth corresponding to the year and nearest latitude. If the observed elongation was east, the true meridian lies on the west of the line which has been found, and makes with it an angle equal to the azimuth. If the elongation was west, the true...