A Compendious System of Practical Surveying, and Dividing of Land: Concisely Defined, Methodically Arranged, and Fully Exemplified : the Whole Adapted for the Easy and Regular Instruction of Youth, in Our American Schools

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T. Hamilton, S. Hilles
Johnson and Warner, 1814 - 227 sider

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Side 222 - Observe, if the true and magnetic amplitudes be both north or both south, their difference is the variation ; but if one be north and the other south, their sum is the variation : and, to know whether it be easterly or westerly, suppose the observer looking towards that point of the compass representing the magnetic amplitude ; then, if the true amplitude be to the right hand of the magnetic, the variation is east, but if to the left hand, it is west.
Side 80 - To the length of the given side ; So is the sine of the angle opposite the required side. To the length of the required side.
Side 52 - ЙО, 30, &c., to the left hand, where it ends at 87 degrees. This line. with the line of equal parts, marked (EP), under it, are used together, and only in Mercator's Sailing. The upper line contains the degrees of the meridian, or latitude in a Mercator's chart, corresponding to the degrees of longitude on the lower line.
Side 221 - . 2. Subtract the Sun's declination from 90«, when the latitude and declination are of the same name, or add it to 90*, when they are of contrary names ; and the sum, or remainder, will be the Sun's polar distance. , 3. Add together the Sun's polar distance, the latitude of the place, and the altitude of the Sun; take the difference between half their sum and the polar distance, and note the remainder. 4. Then add together the log. secant of the altitude ) rejectingtheir the log. secant of the latitude...
Side 53 - ... the remainder will be the logarithm of the quotient. Again, if the logarithm of any number be divided by 2, the quotient will be the logarithm of the square root of that number...
Side 219 - Ъе both north or both south, their difference is the variation ; but if one be north and the other south, their sum is the variation ; and to know whether it be easterly or westerly, suppose the observer looking towards that point of the compass representing the magnetic amplitude : then if the true amplitude be to the right hand of the magnetic amplitude, the variation is east, but if to the left hand, it is west EXAMPLE I. July 3, 1812, in latitude 9° 36' & the Sun was observed to rise E> 32»...
Side 46 - As the figures are increased or diminished in their value, so in like manner must all the intermediate strokes or subdivisions be increased or diminished ; that is, if the first 1 at the left hand be counted 1, then 2 (next following it) will...
Side 42 - BD be a line of chords. 4thly. From the points 10, 20, 30, &c., in the quadrant BD, draw right lines parallel to CD, to cut the radius CB, and they will divide that line into a line of sines which must be numbered from C toward B.

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