XXVII. On the present situation of the magnetic lines of equal variation, and their changes on the terrestrial surface

Abstract

The great progress which has been made within a few years in establishing the laws of magnetic action, as subsisting between magnets on each other, and of these on iron, leads to a rational expectation that the still unknown and mysterious laws of terrestrial variation may by perseverance be likewise elicited. This hope has induced me to undertake the task of collating and arranging all the valuable information recorded in several recent and important voyages and journeys of discovery, surveys, &c., undertaken by the British and by some foreign Governments. In all these cases the officers selected to conduct them have been of the highest scientific character: the subject of magnetism has been, during the time of their performance, the favourite pursuit of many highly talented philosophers in all parts of Europe. Instruments of the most perfect description have been employed, and more than ordinary care bestowed upon the magnetic observations.