Professor Loomis (‘American Journal of Science,’ vol. v. April 1873) considers that a comparison between the mean daily range of the magnetic declination and the number of Auroras observed in each year, and also with the extent of the black spots on the surface of the sun, establishes a connexion between these phenomena, and indicates that auroral displays (at least in the middle latitudes of Europe and America) are subject to a law of periodicity, that their grandest displays are repeated at intervals of about 60 years, and that there are also other fluctuations, less distinctly marked, which succeed each other at an average interval of about 10 or 11 years, the times of maxima corresponding quite remarkably with the maxima of solar spots. [Sidenote: Illustrative table of coincidences.] An illustration of the result of these observations is given on Plate IX. fig. 2. The curves are in close correspondence, and the coincidence at the times of maximum and minimum is remarkable. The auroral maximum generally occurs a little later than the magnetic maximum; and the connexion between the auroral and magnetic curves appears somewhat more intimate than between the auroral and sun-spot curves. [Sidenote: Prof. Loomis considers a sun-spot a solar disturbance affecting the earth’s magnetism.] Professor Loomis contends “that the black spot is a result of a disturbance of the sun’s surface, which is accompanied by an emanation of some influence from the sun, which is almost instantly felt upon the earth in an unusual disturbance of the earth’s magnetism, and a flow of electricity, developing the auroral light in the upper regions of the earth’s atmosphere.” [Sidenote: Carrington and Hodgson’s observations of bright spots on the sun, accompanied by magnetic disturbance at Kew, and followed by wide-spread Auroræ.]