On the annual variation of the magnetic declination, at different periods of the day

In this communication the author has arranged and presented together the Annual variations which the magnetic declination undergoes at every hour of the day at the four Colonial Observatories established by the British government, at Toronto, Hobarton, the Cape of Good Hope and St. Helena. This has been done by means of a graphical representation, in which the annual variations at every hour are shown by vertical lines varying in length according to the amount of the range of the annual variation at each hour; each line having also small cross lines marking the mean positions of the several months in the annual range. The mean declination in the year at the respective hours is marked by a horizontal line which crosses all the verticals at each station. The hours are those of mean solar time at each station, the day commencing at noon.