The theory and practice of surveying. Designed for the use of surveyors and engineers generally, but especially for the use of students in engineering (1886)
Johnson, J. B. (John Butler), 1850-1902 · New York, J. Wiley & sons · leaf 51
tention to this matter. No reliance should be placed on West23°222l201918171615141312 1110 9 87654321012345678 910111 15406080 160020406080 170020406080 180020406080 1900J 1 | | [ | | | | | 1 1 II 1 1 1 1 II I Secular Vdriation\ of the Magnetic Decimation, at Pai is France.. Observed declinations… … Fig. 8. old determinations of the declination unless the rate of changebe known, and even then this rate is not likely to be constant ADJUSTMENT, USE, AND CARE OF INSTRUMENTS. 2$ a great many years. They also show the necessity of record-ing the date and the declination of the needle on all plats…
Surveying
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