 The variation of the magnetic needle in declination, is subject to much irregularity, in some instances increasing, in other decreasing, and some years having scarcely a perceptible motion.  A Manual for Practical Surveyors - Page 57by E. W. Beans - 1854 - 108 pagesFull view - About this book
 | Iowa Engineering Society - Engineering - 1897 - 662 pages
...variations increase in proportion to the distances of the poles on either side of the line of DO variation. The variation of the magnetic needle in declination is subject to much irregularity and some years having scarcely a perceptible motion. At any place there is much irregularity in the... | |
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