Magnetic Observations

Abstract

THE magnetic observations made during 1910 at the Khedivial Observatory, Helwan, are included in a small pamphlet of seven pages, which gives for each month and the year the mean values of the magnetic elements, the diurnal variations in declination, horizontal force and vertical force, and particulars of the ranges of these elements on the eight most disturbed days of the year. In the diurnal variation tables values are given for both midnights, the aperiodic element not being eliminated. This is rather unusual. These tables go to 0-1′ in declination and to 1γ (1 X 10- 5 C.G.S.) in the force components. As the days tabulated in the month average twenty-eight, the expediency of going to 0-01′ and to 0-1γ seems worthy of consideration, especially as the diurnal ranges are small. Disturbances at Helwan, at least in 1910, seem to rule small. The largest ranges in the selected disturbed days were only 13′ in declination, 187γ in horizontal force, and 58γ in vertical force. So far as internal evidence enables one to judge, its magnetic work does increasing credit to the Egyptian Survey Department, and it is to be hoped that it will continue to be prosecuted under favourable conditions.