Observations on days of unusual magnetic disturbance, made at British Colonial Magnetic Observatories, under the Departments of the Ordnance and Admiralty. Part 1.--1840-1841. / Printed ... under the superintendence of ... E. Sabine.

  • Great Britain. Board of Ordnance
Date:
1843
Catalogue details

Licence: Public Domain Mark

Credit: Observations on days of unusual magnetic disturbance, made at British Colonial Magnetic Observatories, under the Departments of the Ordnance and Admiralty. Part 1.--1840-1841. / Printed ... under the superintendence of ... E. Sabine. Source: Wellcome Collection.

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    tend to produce dissimilarity in the proportions, when the amount of disturbance in the same month at the two stations is compared; but as we have already seen the corre- spondence which exists in regard to the days of principal disturbance at both, it may he proper to examine in the first instance the degree in which an accordance may further be traced in the mean monthly fluctuations. 1841. Toronto. Van Diemen Island. Declin« Hor. Force. Declin. Hor. Force. January .... •77 •68 1-00 1-00 February .... 1-18 •75 1-33 1-12 March .... •88 1-02 1-27 1-00 April •75 •82 •75 •88 May •94 •97 •99 TOO June •84 1-03 •66 •70 July •91 •96 •86 •71 August .... 1-46 1-19 1-02 1-08 September 1-30 1-55 •97 1-09 October .... •87 •91 •92 1-09 November •89 1-09 1-11 1*25 December. •93 •96 1-10 •92 The influence of the general disturbances which took place in more than ordinary measure in August, September, and February, is here visible ; April, on the other hand, shows itself to have been a remarkably tranquil month at both stations.* We may still remark, however, even on general inspection, an indication of the apparent influence of season, which becomes more manifest when the months are arranged according to the respective seasons. Toronto. Van Diemen Island. Mean. Declin. Hor. Force. Declin. Hor. Force. 4 Summer Months 1-05 1 -04 1-13 ro7 1-07 4 Winter Months 0-94 0-87 0-88 0-87 0-89 4 Months (2 Spring & 2 Autumn) . 0-94 1-07 0-98 1-01 1-00 The excess of the proportionate fluctuation in the summer over the winter months, in both elements, and at both stations, is too consistent and considerable to be altogether regarded as accidental, and is more deserving of attention when it is remembered that it must be viewed as a residual quantity after the counter-action of the causes, the syn- * At Prague, in April, no day occurred in which the sum of the fluctuations of the Declination equalled twice the sum of the fluctuations of the mean monthly positions at the same hours; consequently, according to M. Kreil’s mode of characterizing disturbed days, there was no day of disturbance of the Declination at Prague in the month of April.