III. On the lunar-diurnal variation of the magnetic declination obtained from the Kew photograms in the Years 1858, 1859, and 1860

Abstract Having communicated to the Royal Society in a recent paper an analysis of the disturbances of the declination in the years 1858 and 1859, shown by the photograms of the Kew Observatory, I propose in the present paper to submit the results of the lunar-diurnal variation of the declination in the years 1858, 1859, and 1860, obtained from the same source. The directions of the declination magnet at the instant of the commencement of every solar-hour having been tabulated from the photograms, and the final normals for each month and hour computed, after the omission from the record of all the hourly directions which deviated 3'·3 from their final normals,—the differences were taken between each of the remaining hourly directions and the final normal of the same month and hour, and were entered afresh in lunar monthly tables, having the lunar days in successive horizontal lines, and the twenty-four lunar hours in vertical columns, each difference being placed under the lunar hour to which it most nearly approximated.