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.

    7/140
    PREFACE. As the principal interest of the Observations, made during periods of magnetic disturb- ance, appears likely to proceed from their being viewed in connexion with similar observations made simultaneously in other parts of the globe, it has been considered desirable to separate the observations made at such times, from those which are made daily at stated intervals, and to print them in a volume by themselves; and by bringing together the observations of the same date, at the several Observatories, and arranging them in chronological order, to furnish the opportunity of more readily comparing them with each other, and with contemporaneous observations published elsewhere. It is intended that this volume shall comprise the disturbance observations made from 1840 to 1845 inclusive, at the Colonial Observatories instituted by the British Govern- ment; the part of the volume which is now published, contains those of 1840-1841. In addition to the extra observations made at short intervals when the disturbance of the magnets was excessive, the regular observations (which are made hourly at some of the Observatories, and two-hourly at others,) have been extracted from the registers for the days of disturbance, and subjoined; being given for all the Observatories on all days on which extra observations were made at any one. The mean monthly positions of the magnets at the hours of regular observation have also been given, for the purpose of furnishing approximate normal positions, with which the observations on days of dis- turbance may be compared. In the hope that an early publication of the observations in 1840-1841, and their comparison with simultaneous observations in other parts of the globe, may lead to the suggestion of more specific points of enquiry than are at present apprehended, and possibly to the substitution of improved instruments and modes of observation,—the printing of this part of the volume has been proceeded with, although all the materials required for the complete reduction of the observations have not yet been received. The coefficients are still wanting for the temperature corrections of the Horizontal and Vertical F'orce observations of the Antarctic Expedition and of the Van Diemen Island Observatory, and of the Vertical Force observations at St. Helena and the Cape of Good Hope, the neces- sary experiments for their determination not having yet been made. The scale coefficients A 2