Having at length completed the analysis of the larger disturbances of the horizontal and vertical magnetic forces at Toronto during five years of hourly observation, with a view to the development of the periodical laws which regulate the occurrence of the occasional disturbances of those elements, and of their theoretical equivalents, the Inclination and Total Force, I now propose to lay before the Royal Society a condensed view of the mode in which the investigation has been made, and of its results. The hourly observations of the Bifilar and Vertical Force Magnetometers during the five years terminating June 30, 1848, were received at Woolwich, from Toronto, precisely in the state in which they are printed in the second and third volumes of the 'Observations at the Toronto Observatory'; namely, the readings, uncorrected for temperature, at every hour of Göttingen time, arranged in Monthly tables, accompanied by corresponding tables of the temperature of the magnets, shown by thermometers of which the balls were enclosed in the same case with the magnets, and which were read contemporaneously with the Bifilar and Vertical Force scales. The Monthly tables of the scale-readings and of the temperatures were summed before their transmission to Woolwich, both in vertical and horizontal columns, and means were taken of all the days in the month at the different hours, and of all the hours of the day on the different days, forming "hourly means” and "daily means.” In this state the observations were received at Woolwich and subsequently printed; they were, in fact, printed from the original manuscripts.