XXIII.—On the Horizontal Force of the Earth's Magnetism

Abstract

The only observations made with Dr Lloyd's bifilar magnetometer, published with corrections applied to the individual observations, are those made in the Makerstoun Observatory, forming part of the Transactions of the Royal Society of Edinburgh. The results obtained from these observations (especially from those for 1844 and 1845), were first compared by me in 1856, with observations (also corrected by myself) made in the Trevandrum Observatory during the same years. The singular resemblance of the variations of daily mean intensity thus discovered at two places so distant, and so differently situated on the earth's surface, induced me to undertake the considerable labour of determining the temperature coefficients, and of correcting and discussing all the published (and some unpublished) observations made in the colonial observatories. This labour was too great to have been undertaken by me alone, in consistence with my other duties, and it is due to the liberality of His Highness the Rajah of Travancore, that I could employ in part for this work the computers attached to his Observatory.