Contributions to Terrestrial Magnetism Volume 2

Contributions to Terrestrial Magnetism Volume 2

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1846 edition. Excerpt: ...c=017; rf=l'026. "From these values of a, b, c and d, a table of corrections was found by means of equations (12.) and (13.) (Contribution V.), employing calculated values of "In order to test the accuracy of the table, we may compare observed and calculated values of the dip at King George's Sound. It will be seen that on the northerly points the correction is rather too large, on the easterly and westerly too small, and nearly correct on the S., S.S.W. and S.S.E. points. The differences however are within the limits of observation errors. The mean inclination observed on shore with the same needle being--65 11'. t 3. Calculation of Corrections for Intensity Observations. "The constant A is calculated from the above observations by means of the formula sin=ccos 6cos -- sin0. "The values of $, p' and are all given by the observations on the sixteen points of the compass; those of p and 6 by the observations on shore. The following are the resulting values for A', viz.--King George's Sound... A'=0-998 Mauritius A'=0992 Cape of Good Hope.... A'=0-992 Mean.. A'=0994 "This value being so near unity, A is assumed =1-0, with which and the values of c and d already determined, a table of corrections was formed by means of the equation =A'c( tan 0+cos cos 6 cosec &, 0 and being obtained from the tables for correcting the dips and declinations. Philosophical Transactions, 1843, Part II. p. 162. "II. Determination nf Index Corrections. "1. Decimation Observations. "The compass used was one of the Admiralty compasses (B. 20). It was supplied with two cards, one considerably heavier than the other to be used in bad weather; but as it was found that in all weathers the heavy card was the...show more

Product details

  • Paperback | 82 pages
  • 189 x 246 x 4mm | 163g
  • Rarebooksclub.com
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236523083
  • 9781236523082