# A Manual of Topographical Drawing

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Page 107 - Lay off by scale RS = 14.4 yards, call S 9, and lay off 9 — 8, 8 — 7, etc., each equal to 4.5 yards. The scale of slope is complete. PROBLEMS. To determine the slope of a line, having given its projection and the references of two of its points. The slope of a line is the angle which it makes with its projection on the plane of reference. It is expressed by dividing the difference of reference of any two of its points by the number expressing the length of the projection between these two points....
Page 103 - PROBLEM 3. To Construct a Square that shall be in any proportion to a given Square. Let ABC D (Fig. 56) be the given square. It is required to construct a square which shall be to ABCD as 2 is to 5. Upon the side AB as a diameter, describe the semicircle AGB, and divide the line AB into five equal parts. At the second point of division, erect the perpendicular FG, and join A G. The square described upon AG will be to the given square ABCDas2isto<V the square described FIQ.
Page 87 - ... one-seventh being sometimes used. The following table, taken from the last edition of Lieut. Smith's Topographical Drawing, will serve as a guide in proportioning capital letters : " Taking the extreme width of H, measured across the middle, or exclusive of the caps, as the unit, the widths of the other letters, or of their characteristic parts, may be expressed approximately by the numbers in the third column of the table. In case of letters having oblique lines, these widths are to be taken...
Page 36 - Lay off on the middle parallel, eastward and westward from the central meridian, spaces corresponding to degrees, or smaller divisions of longitude, as the case may require, and through these points of division and the apex of the cone draw straight lines. These will be the meridians required. 70. But it is rarely possible to connect the map with the apex of the cone. In such cases, therefore, the points of intersection (and other points, if needed) on the middle parallel must be platted by rectangular...
Page 18 - On a scale of one inch to a mile, or ^-3^0, besides these, farms, woods, isolated buildings, every stream of 600 feet in length, and every hill of 100 feet in height, can be represented. On a scale of two inches to a mile, or...
Page 64 - To find the ratio of black to white for any given slope : Subtract the given inclination from 45° for a denominator, and take the given inclination for a numerator, and we shall have the.
Page 103 - CF will be four times the square ABCD ; and so for any multiple of the square ABC D.